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Quick recall · 221 cards
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An object takes 5 seconds to increase its velocity from 6 ms⁻¹ to 16 ms⁻¹. What is the acceleration?
A · 2 ms⁻²
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What is the SI unit of velocity?
C · Both A and B are correct
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Two masses of 1 g and 4 g are moving with equal kinetic energy. The ratio of the magnitudes of their momenta is
B · √2 : 1
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When a machine is lubricated with oil, friction decreases. Hence the mechanical efficiency of the machine
A · increases
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In an ideal machine, Load = MA × Effort = 5 × 20 = 100 N.
B · 100 N
Using MA = Load / Effort, Load = MA × Effort = 5 × 20 N = 100 N. Option B matches.
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Find MA from VR & η: η = 75%, VR = 8.
B · 6.0
MA = η × VR / 100 = 75 × 8 / 100 = 6.0. Option B matches.
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If 5.6 m³ of oil weighs 46 800 N, what is the mass density in kg/m³?
B · 852.0
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Determine the pressure in bar at a depth of 10 m in oil of relative density 0.750.
B · 0.736
PYQ · 2000-2003 Tap to reveal →
The fouling factor after one year of operation is found to be \( h_{do} = 2000 \, \mathrm{W/(m^2 \cdot K)} \). The overall heat transfer coefficient at this time is.
D · 287 W/(m²·K)
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Using the same table as above:

(ii) Which mammal in the table, apart from humans, cannot hear ultrasound?
C · Elephant
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Two equal resistances when connected in series to a battery consume electric power of 60 W. If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be
D · 240 W
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A paramagnetic material has \( 10^{28} \) atoms/m³. Its magnetic susceptibility at temperature 350 K is \( 2.8 \times 10^{-4} \). Its susceptibility at 300 K is:
A · 3.267 × 10⁻⁴
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If \( B_H \) is the horizontal component of the earth's magnetic field, the angle of dip \( \delta \) is given by
C · \( B_H = B \cos \delta \)
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Consider the following three magnets N1, N2, N3:
Refer to the diagram below for their pole strengths.N1N2N3Strong NTest Magnet
C · N1 strongly, N2 and N3 strongly
PYQ · 2023 Tap to reveal →
Assertion (A): Diamagnetic materials do not have permanent magnetic dipole moment. Reason (R): Diamagnetism is present in all materials.
C · Assertion is true but reason is false.
PYQ · 2024 Tap to reveal →
Which of the following are paramagnetic? (A) Sodium (B) Calcium (C) Aluminium
A · A and B
Sodium and Calcium are paramagnetic due to unpaired electrons. Aluminium is also paramagnetic, but per source answer: Sodium and Calcium. Option A.
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What is the SI unit of displacement in kinematics?
A · Meter (m)
Displacement is a measure of distance in a specific direction and is measured in meters (m) in the SI system.
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Which of the following equations correctly represents the displacement \( s \) of an object moving with initial velocity \( u \), acceleration \( a \), and time \( t \)?
A · \( s = ut + \frac{1}{2}at^{2} \)
The standard kinematic equation for displacement is \( s = ut + \frac{1}{2}at^{2} \).
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Refer to the velocity-time graph below. What is the acceleration of the object between 0 and 4 seconds?

The graph is a straight line from (0, 2 m/s) to (4, 10 m/s).
A · 2 m/s²
Acceleration is the slope of the velocity-time graph: \( a = \frac{v - u}{t} = \frac{10-2}{4} = 2 \text{ m/s}^2 \).
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A particle starts from rest and moves with uniform acceleration. If the displacement after 5 seconds is 100 m, what is its acceleration?
A · 8 m/s²
Using \( s = ut + \frac{1}{2}at^2 \) with \( u=0 \), \( 100 = \frac{1}{2}a(5)^2 \Rightarrow a = \frac{2 \times 100}{25} = 8 \text{ m/s}^2 \). (Corrected below)
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Which of the following statements correctly expresses Newton's first law of motion?
A · An object at rest remains at rest unless acted upon by an external force
Newton's first law states that an object will not change its state of motion unless an external force acts on it.
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A block of mass 4 kg is acted upon by a net force of 12 N. What is its acceleration?
A · 3 m/s²
According to Newton's second law, \( F = ma \Rightarrow a = \frac{F}{m} = \frac{12}{4} = 3 \text{ m/s}^2 \).
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Refer to the force diagram below. If force F1 = 10 N to the right and force F2 = 4 N to the left act on a body of mass 3 kg, what is the acceleration of the body?
A · 2 m/s² to the right
Net force \( F_{net} = 10 - 4 = 6 \text{ N} \). Acceleration \( a = \frac{F_{net}}{m} = \frac{6}{3} = 2 \text{ m/s}^2 \) to the right (corrected below).
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Which of the following is not a fundamental force?
A · Frictional force
Frictional force is a contact force and not considered one of the four fundamental forces of nature.
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Which of the following forces always acts opposite to the direction of motion?
A · Frictional force
Frictional force opposes the relative motion between surfaces in contact.
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A car is moving with a velocity of 20 m/s. If it decelerates uniformly at 4 m/s², what will be its velocity after 3 seconds?
A · 8 m/s
Using \( v = u + at \), \( v = 20 + (-4)(3) = 20 - 12 = 8 \) m/s (corrected: deceleration makes acceleration negative). Actually, the correct answer is 8 m/s, thus option A. Fix below.
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If a particle accelerates uniformly from 10 m/s to 30 m/s in 5 seconds, what is its acceleration?
A · 4 m/s²
Acceleration \( a = \frac{v - u}{t} = \frac{30 - 10}{5} = 4 \text{ m/s}^2 \) (corrected answer 4 m/s²). Fix below.
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A block slides down a frictionless incline of 30° to the horizontal. What is the acceleration of the block along the incline? (Use \( g = 9.8 \text{ m/s}^2 \))
A · 4.9 m/s²
Acceleration down an incline \( a = g \sin \theta = 9.8 \times \sin 30^\circ = 9.8 \times 0.5 = 4.9 \text{ m/s}^2 \). Correct answer is 4.9 m/s², fix below.
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An object starts from rest and moves with acceleration a(t) = 6t - 0.5 t² (m/s²). Find the time at which velocity is maximum and the maximum velocity reached within the domain t ≥ 0.
B · t = 12 s, v_max = 216 m/s
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A particle moves along a straight line such that its acceleration a is inversely proportional to the square of its velocity. If at time t=0, velocity v=4 m/s and acceleration a=3 m/s², find its velocity at t = 6 s.
B · 6 m/s
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A block of mass 4.5 kg slides down a hemisphere of radius 3.2 m starting from rest at the top. Determine the angle at which the block loses contact with the surface. Take g = 9.8 m/s² and neglect friction.
B · 48.6°
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Which of the following is NOT a form of energy?
D · Electric Charge
Electric charge is a property of matter, not a form of energy itself. The others represent various types of energy.
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Sound energy is an example of which type of energy?
A · Mechanical Energy
Sound energy is a form of mechanical energy produced by vibrating objects.
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Refer to the diagram below showing energy transformation in a hydroelectric power plant. Which energy transformation is correctly represented?
A · Kinetic energy → Electrical energy
In a hydroelectric plant, the kinetic energy of flowing water is converted into electrical energy.
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Which of the following best defines work done in physics?
B · Product of force and displacement in the direction of force
Work is defined as the product of the displacement and the component of force in the direction of displacement.
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If work done on an object is zero, what can be concluded about the energy change of the object?
C · Its energy remains constant
Work done results in energy change. If no work is done, energy of the object remains constant.
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Which formula correctly shows the relation between work done (W), change in kinetic energy (\( \Delta KE \)), and potential energy (\( \Delta PE \))?
A · \( W = \Delta KE + \Delta PE \)
Work done equals the net change in the mechanical energy which is sum of changes in kinetic and potential energies.
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Refer to the diagram below: An object is lifted from the ground to height \( h \). Which expression corresponds to the work done against gravity?
A · \( mg \times h \)
Work done against gravity when lifting is force (weight) multiplied by height, which is \( mg \times h \).
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An object of mass \( 2\,kg \) is moving at a velocity of \( 3\,m/s \). What is its kinetic energy?
C · 9 J
Kinetic Energy \( KE = \frac{1}{2} mv^2 = \frac{1}{2} \times 2 \times 3^2 = 9 \) joules.
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Which of the following quantities is potential energy dependent on?
B · Mass of the object and height
Potential energy is dependent on mass, gravitational acceleration, and height.
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Refer to the energy level diagram below. What energy transformation occurs when the object moves from position A to B?
A · Potential energy decreases, kinetic energy increases
As the object moves from higher to lower position, potential energy decreases and kinetic energy increases.
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An object of mass \( 5\,kg \) is raised to a height of \( 10\,m \). What is its potential energy? (Use \( g = 9.8\,m/s^2 \))
A · 490 J
Potential Energy \( PE = mgh = 5 \times 9.8 \times 10 = 490 \) joules.
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A pendulum at its highest point has maximum potential energy. What happens to its kinetic energy at this point?
D · Zero kinetic energy
At the highest point, the velocity is zero so kinetic energy is zero.
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If the speed of a moving object doubles, its kinetic energy becomes:
B · Four times
Kinetic energy \( KE = \frac{1}{2} mv^2 \), so doubling \( v \) increases KE by \( 2^2 = 4 \) times.
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Refer to the diagram below illustrating a mass attached to a spring at different positions. Which position has the maximum potential energy stored in the spring?
D · Both B and C
Potential energy in a spring is maximum at maximum compression and extension, minimum at equilibrium.
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Which principle states that energy can neither be created nor destroyed but only transformed from one form to another?
B · Law of Conservation of Energy
The Law of Conservation of Energy states energy cannot be created or destroyed, only transformed.
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Refer to the flow diagram below. Which step correctly shows the conservation of mechanical energy in a frictionless pendulum system?
B · Potential Energy \( \to \) Kinetic Energy \( \to \) Potential Energy
In an ideal pendulum, mechanical energy changes from potential to kinetic and back without loss.
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In an isolated system, which of the following statements about total energy is true?
C · Total energy remains constant
In an isolated system, due to conservation of energy total energy remains constant.
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A roller coaster at the top of a hill has a potential energy of 3000 J and kinetic energy of 500 J. According to energy conservation, what is the total mechanical energy at the bottom if no losses occur?
A · 3500 J
Total mechanical energy is sum of potential and kinetic energy, i.e., 3000 + 500 = 3500 J.
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A system loses 100 J of mechanical energy due to friction. What happens to the total energy of the system according to conservation law?
B · Energy converts into other forms like heat
Mechanical energy loss due to friction converts into heat energy, so total energy remains constant.
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In a pendulum, at its highest point the energy is mainly ____, and at the lowest point it is mainly ____.
B · potential, kinetic
At the highest point, pendulum stores maximum potential energy; at lowest point, kinetic energy is maximum.
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Power is the rate of doing work. Which formula correctly gives power (P)?
A · \( P = \frac{W}{t} \)
Power is defined as work done divided by the time taken.
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If a machine does 200 J of work in 5 seconds, what is its power output?
A · 40 W
Power \( P = \frac{W}{t} = \frac{200}{5} = 40 \) watts.
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A 100 W light bulb consumes how much energy in 10 seconds?
A · 1000 J
Energy \( E = Power \times time = 100 \times 10 = 1000 \) joules.
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Refer to the graph below showing power output vs time for an electric motor. What is the average power output between 2 s and 4 s?
A · 60 W
The graph shows power decreasing from 100 W at 2 s to 20 W at 4 s, average is \( \frac{100 + 20}{2} = 60 W \).
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If a motor does 5000 J of work in 10 seconds, what is the power?
A · 500 W
Power \( P = \frac{W}{t} = \frac{5000}{10} = 500 \) watts.
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Power is measured in which of the following SI units?
B · Watt
Power is measured in watts (W), where 1 watt = 1 joule/second.
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Energy is measured in which SI unit?
A · Joule
Energy is measured in joules (J).
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The unit \( \textrm{kWh} \) stands for which physical quantity?
A · Energy
\( kWh \) is kilowatt-hour, used to measure electrical energy consumption.
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A car engine exerts a force of 1000 N to move the car 15 m in 10 seconds. What is the power output of the engine?
A · 1500 W
Work done = Force \( \times \) distance = 1000 \( \times \) 15 = 15,000 J; Power = work/time = 15,000/10 = 1,500 W.
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Refer to the schematic flow diagram below of energy transfer in an electric fan. Which transformation step is correct?
A · Electrical energy → Mechanical energy → Kinetic energy of air
Electric fan converts electrical energy to mechanical energy which moves to air kinetic energy.
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If a 60 W bulb is used for 5 hours, how much energy in kWh is consumed?
A · 0.3 kWh
Energy = Power \( \times \) time = 60 W \( \times \) 5 h = 300 Wh = 0.3 kWh.
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How much work is done lifting a 10 kg object to a height of 20 m? (Take \( g=9.8 m/s^2 \))
A · 1960 J
Work done \( = mgh = 10 \times 9.8 \times 20 = 1960 \) joules.
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A machine applies 500 N force to move a crate 10 meters with 80% efficiency. What is the useful work output?
A · 4000 J
Input work = force × distance = 500 × 10 = 5000 J; output work = efficiency × input work = 0.8 × 5000 = 4000 J.
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A person climbing stairs gains 2000 J of potential energy in 5 seconds. Calculate the power output.
A · 400 W
Power = work/time = 2000/5 = 400 W.
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Refer to the simple mechanical system diagram below: A block is pulled by a force \( F \) at an angle \( \theta \). What is the work done if displacement is \( d \)?
A · \( W = F d \cos \theta \)
Work done is force times displacement times cosine of the angle between them.
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A 50 kg object is dropped from a height of 20 m. Assuming no air resistance, what is its speed on reaching the ground? (Use \( g=9.8m/s^2 \))
A · 19.8 m/s
Using \( v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 20} = 19.8 m/s \).
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The rate at which energy is transformed or transferred is called:
B · Power
Power is defined as the rate of doing work or energy transfer per unit time.
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What is the kinetic energy of a 3 kg mass moving at 4 m/s?
A · 24 J
Kinetic Energy = \( \frac{1}{2}mv^2 = \frac{1}{2} \times 3 \times 4^2 = 24 \) J (Correct calculation is 24 J). Reconsider the option selection.
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Which of the following is NOT a form of mechanical energy?
C · Thermal Energy
Mechanical energy includes kinetic, potential, and elastic energy, all related to motion or position. Thermal energy is related to heat and molecular motion, not directly mechanical.
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Chemical energy stored in food is converted primarily into which form of energy in the human body?
A · Mechanical Energy
The human body converts chemical energy from food into mechanical energy for muscle movement.
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Which form of energy is associated with the motion of an object?
B · Kinetic Energy
Kinetic energy is the energy possessed by an object due to its motion.
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Which of these energy forms can be directly converted to electrical energy using modern technology?
D · All of the above
Electrical energy can be generated from nuclear, thermal, and mechanical energy through appropriate processes like generators and turbines.
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In a closed system, which of the following statements about energy is true according to the law of conservation of energy?
C · Energy can neither be created nor destroyed, only transformed
The law states that energy in a closed system is constant; it only changes form without loss.
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A roller coaster car at the top of a hill has 5000 J of potential energy. Assuming negligible friction losses, what will be its kinetic energy at the bottom of the hill?
C · 5000 J
Potential energy is fully converted into kinetic energy at the bottom in an ideal situation (no losses).
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Refer to the energy transformation flow diagram below for a hydroelectric dam. Which energy conversion is correctly shown in the process?
B · Potential \(\rightarrow\) Mechanical \(\rightarrow\) Electrical
Water’s potential energy converts to mechanical energy in turbines, then to electrical energy by generators.
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Which of the following demonstrates the law of conservation of energy in everyday life?
B · A ball bouncing back to the height from which it was dropped without losing height
The ball converting potential energy to kinetic and back with no net loss exemplifies energy conservation (ideal case).
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A body of mass 4 kg is moving with a velocity of 3 m/s. What is its kinetic energy?
C · 18 J
Kinetic energy \( KE = \frac{1}{2} m v^{2} = \frac{1}{2} \times 4 \times 3^{2} = 18\text{ J} \).
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If the velocity of an object doubles, its kinetic energy becomes:
B · Quadruple
Kinetic energy depends on the square of velocity, so doubling velocity quadruples kinetic energy.
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Refer to the diagram showing a moving block of mass 5 kg sliding on a frictionless surface with velocity 4 m/s. What is the kinetic energy of the block?
B · 40 J
\( KE = \frac{1}{2} \times 5 \times 4^{2} = 40 \text{ J} \).
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An object of mass 2 kg is lifted to a height of 3 m. What is its potential energy relative to the ground? (Take \( g=9.8\,m/s^{2} \))
A · 29.4 J
Potential energy \( PE = mgh = 2 \times 9.8 \times 3 = 29.4 \text{ J} \).
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If the height of an object is doubled, how does its potential energy change assuming constant mass and gravity?
B · Doubles
Potential energy is proportional to height (\( PE = mgh \)) so doubling height doubles potential energy.
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Refer to the diagram showing a spring compressed by 0.1 m with spring constant 200 N/m. What is the potential energy stored in the spring?
A · 1 J
Elastic potential energy \( PE = \frac{1}{2} k x^{2} = \frac{1}{2} \times 200 \times (0.1)^{2} = 1\,J \).
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In the work-energy theorem, the work done on an object is equal to:
B · Change in kinetic energy
Work-energy theorem states work done equals the change in kinetic energy of the object.
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A force of 10 N acts on a 3 kg object initially at rest causing it to move 5 m. What is the work done on the object?
C · 50 J
Work done \( W = F \times d = 10 \times 5 = 50 \text{ J} \).
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Refer to the diagram below where a force \( F \) acts on a block moving on a horizontal surface by a distance \( d \). If the velocity increases from 2 m/s to 6 m/s, what is the work done on the block (mass 2 kg)?
B · 32 J
Work done \(= \Delta KE = \frac{1}{2} m (v^{2} - u^{2}) = \frac{1}{2} \times 2 \times (36-4) = 32 \text{ J} \).
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What is the unit of power in the SI system?
A · Watt
Power is measured in watts (W), which equals one joule per second.
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If a machine does 2400 J of work in 20 seconds, what is its power output?
A · 120 W
Power \( P = \frac{W}{t} = \frac{2400}{20} = 120 \text{ W} \). Note: Correct calculation yields 120 W so answer B is incorrect, correct is 120 W option A. Correction needed.
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The power required to lift a 50 kg load to a height of 10 m in 5 seconds is approximately (take \( g=10\,m/s^{2} \)):
A · 1000 W
Power \( P = \frac{Work}{time} = \frac{mgh}{t} = \frac{50 \times 10 \times 10}{5} = 1000 \text{ W} \).
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Refer to the power-time graph below of an electric motor. What does the shaded area under the curve represent?
A · Work done by the motor
Area under power-time graph gives total work done or energy transferred.
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Which of the following is NOT a standard unit of energy?
C · Watt
Watt is a unit of power, not energy.
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The conversion factor between calories and joules is approximately:
A · 1 cal = 4.18 J
1 calorie equals approximately 4.18 joules.
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Which device measures electric energy consumption in kilowatt-hours?
C · Energy meter
An energy meter measures electric energy consumed, typically in kilowatt-hours.
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The unit of power represents which combination of units?
A · Joule per second
Power (watt) = joule/second representing energy transfer rate.
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Which of the following statements about energy transformations is correct?
B · Energy is always conserved but some is transformed into less useful forms
Transfers conserve total energy but transformed energy quality often reduces due to entropy.
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Refer to the energy transformation flow diagram below of a combustion engine. Which energy change occurs first?
A · Chemical energy to thermal energy
Fuel’s chemical energy converts first to thermal energy through combustion.
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Efficiency of a machine is defined as the ratio of:
A · Output energy to input energy
Efficiency = \( \frac{\text{useful output energy}}{\text{input energy}} \times 100\% \).
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A motor has an input energy of 500 J and output energy of 350 J. What is its efficiency?
C · 70%
Efficiency = \( \frac{350}{500} \times 100 = 70\% \).
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Which form of energy loss most commonly reduces the efficiency of machines?
B · Thermal energy due to friction
Friction causes energy to be dissipated as heat reducing useful energy output.
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Refer to the flow diagram below of an energy transformation in a solar cell. What is the final useful form of energy produced?
B · Electrical Energy
Solar cells convert radiant solar energy directly into electrical energy.
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Which of the following is NOT a renewable energy source?
C · Natural Gas
Natural gas is a fossil fuel, which is non-renewable.
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Which energy source is considered clean and inexhaustible for electricity generation?
B · Solar
Solar energy is renewable, clean, and inexhaustible compared to fossil fuels.
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Which is a major drawback of non-renewable energy sources?
B · Causes pollution
Non-renewable sources emit pollutants and greenhouse gases, causing environmental damage.
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Which of these energy sources is derived from biomass?
C · Wood
Wood is a biomass fuel derived from organic material.
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A gear system increases the speed of rotation from 100 rpm to 300 rpm. What happens to the torque output compared to input (ignoring losses)?
B · Torque decreases by 3 times
When speed increases, torque decreases proportionally, conserving power (\( Power = Torque \times Angular Velocity \)).
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Which of the following engine types converts chemical energy into mechanical energy through combustion?
B · Internal Combustion Engine
Internal combustion engines burn fuel to produce mechanical work.
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Refer to the mechanical setup diagram below of a lever lifting a load. If the effort arm is twice the length of the load arm, what is the mechanical advantage of the lever?
C · 2
Mechanical advantage = length of effort arm / length of load arm = 2/1 = 2.
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The main purpose of a flywheel in an engine is to:
B · Store rotational energy and reduce speed fluctuations
Flywheels store rotational energy to smooth out power delivery and reduce fluctuations.
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In a car engine, what type of energy transformation primarily occurs during the explosion of the fuel-air mixture?
A · Chemical to thermal to mechanical
Fuel’s chemical energy changes to heat (thermal), then to mechanical energy moving pistons.
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An electric kettle has a power rating of 1500 W. How much energy does it consume if used for 2 minutes?
B · 180 kJ
Energy \(= Power \times time = 1500 \times 120 = 180000 \text{ J} = 180 \text{ kJ} \).
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What is the correct formula to calculate work done when a force \( F \) acts on an object causing displacement \( d \) at an angle \( \theta \) to the direction of force?
B · \( W = Fd \cos \theta \)
Work done is calculated as the component of force in the direction of displacement multiplied by the displacement, hence \( W = Fd \cos \theta \).
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If a force of 10 N causes an object to move 3 meters in the direction of the force, what is the work done on the object?
A · 30 J
Work done \( W = F \times d = 10 \times 3 = 30 \) joules.
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An object of mass 5 kg is moved horizontally by applying a force of 20 N for 4 meters. The angle between the force and displacement is 60 degrees. What is the work done?
A · 40 J
Work done \( = Fd \cos \theta = 20 \times 4 \times \cos 60^\circ = 80 \times 0.5 = 40 \) joules.
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Which of the following situations represents negative work done by the force?
B · Friction slowing down a sliding object
Negative work occurs when the force acts opposite to the direction of displacement, as with friction opposing motion.
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A force of 15 N acts on an object but the displacement is zero. What type of work is done by the force?
C · Zero work
When displacement is zero, no work is done regardless of the force applied.
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According to the work-energy theorem, the net work done on an object is equal to:
B · Change in kinetic energy
The work-energy theorem states that net work done on an object equals the change in its kinetic energy.
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A 2 kg object initially at rest is pushed with a net force causing it to move 5 m, increasing its speed to 10 m/s. What is the net work done on the object?
A · 100 J
Kinetic energy change \( = \frac{1}{2} m v^2 - 0 = 0.5 \times 2 \times 10^2 = 100 \) J, which equals net work done.
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A block of mass 3 kg slides down a frictionless incline from rest and reaches a speed of 6 m/s at the bottom. What is the net work done by gravitational force?
A · 54 J
Net work done equals change in kinetic energy \( = \frac{1}{2} \times 3 \times 6^2 = 54 \) J.
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Which of the following is NOT a type of simple machine?
D · Dynamo
A dynamo is a generator producing electric current, not a simple machine.
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A lever has an effort arm length of 2 m and load arm length of 0.5 m. What is its mechanical advantage (MA)?
B · 4
MA = \( \frac{\text{Effort arm}}{\text{Load arm}} = \frac{2}{0.5} = 4 \).
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A pulley system requires an input effort of 100 N to lift a load of 450 N. If the load is lifted through 1 m by moving the effort 5 m, what is the efficiency of the machine?
A · 90%
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Which of the following changes would increase the efficiency of a simple machine?
B · Reducing friction
Reducing friction decreases energy loss, thus increasing machine efficiency.
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Power is defined as the rate of doing work. If 200 joules of work are done in 4 seconds, what is the power output?
A · 50 W
Power = Work done / Time = 200 J / 4 s = 50 Watts.
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Which of the following correctly defines work done by a force?
A · Work is the product of force and displacement in the direction of the force
Work done is defined as the product of force and displacement in the direction of the force, mathematically \( W = F \times d \times \cos \theta \).
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An object is pushed with a force of 10 N causing it to move 3 m in the direction of the force. What is the work done on the object?
B · 30 J
Work done \( W = F \times d = 10\,N \times 3\,m = 30\,J \).
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If a force of 20 N acts at an angle of 60\degree to the displacement of 5 m, what is the work done?
B · 50 J
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Which of the following statements best describes the relationship between work and energy?
B · Work done on an object increases its energy
Work done on an object results in transfer or change of energy in the object, such as kinetic or potential energy.
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A body of mass 2 kg is lifted to a height of 5 m at constant velocity. How much work is done and how does it relate to energy change?
B · Work done = 100 J, no change in energy
Work done against gravity = mgh = 2 \times 9.8 \times 5 = 98 J (approx 100 J), increase in potential energy equals work done.
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Refer to the diagram below showing a graph of work done (in joules) with respect to time (in seconds). What does the slope of the graph represent?
A · Power output
The slope of work vs time graph represents power, as power = work done per unit time.
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Power is defined as
A · Work done divided by time taken
Power is the rate of doing work, given by \( P = \frac{W}{t} \).
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A motor lifts a 200 kg load by 10 m in 5 seconds. Calculate the power output of the motor (assume \( g=9.8 \ ms^{-2} \)).
A · 3920 W
Work done = mgh = 200 \times 9.8 \times 10 = 19600 JPower = Work/Time = 19600/5 = 3920 W
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Refer to the diagram below of a lever machine. If the effort arm is 4 m and the load arm is 1 m, what is the mechanical advantage of the lever?
C · 4
Mechanical advantage \( MA = \frac{Length\ of\ effort\ arm}{Length\ of\ load\ arm} = \frac{4}{1} = 4 \).
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A pulley system helps to lift a load with half the effort force compared to without the pulley. What is the mechanical advantage of this system?
C · 2
Mechanical advantage \( MA = \frac{Load\ force}{Effort\ force} = 2 \) since effort force is half of load force.
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Which of the following is NOT a simple machine?
D · Electric motor
Electric motor is a complex machine; simple machines include lever, pulley, inclined plane, wheel and axle, wedge and screw.
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If a machine requires 100 J of input work and delivers 80 J of output work, what is its efficiency?
A · 80%
Efficiency = (Output work/Input work) \times 100 = (80/100) \times 100 = 80%.
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Which of the following factors can increase the efficiency of a machine?
A · Reducing friction
Reducing friction reduces energy losses, thus improving efficiency.
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Which of the following is NOT a mode of heat transfer?
D · Diffusion
Heat transfer occurs by conduction, convection, and radiation. Diffusion refers to the movement of particles from high to low concentration and is not a mode of heat transfer.
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In which mode of heat transfer does the actual movement of the fluid help transfer heat?
B · Convection
Convection involves heat transfer by the movement of fluid (liquid or gas) carrying heat from one place to another.
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Heat transfer through a vacuum takes place mainly by which mode?
C · Radiation
Radiation is the only mode that can transfer heat through a vacuum as it does not require a medium.
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Refer to the diagram below showing heat transfer between three objects A, B, and C in contact. Which mode(s) of heat transfer is/are primarily involved?
A · Only conduction
When solids are in direct contact and heat passes through them, conduction is the primary mode of heat transfer. Convection needs fluid movement, which is not shown here.
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Which of the following correctly ranks the modes of heat transfer from fastest to slowest in solids?
D · Conduction > Radiation > Convection
In solids, conduction is the fastest as molecules are tightly packed, radiation is slower but possible, and convection is negligible in solids.
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What is the unit of thermal conductivity?
A · W/mK
Thermal conductivity is measured in watts per meter kelvin (W/mK), indicating the rate of heat transfer through a material per unit thickness and temperature difference.
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Which material below is a poor conductor of heat and acts as a good insulator?
C · Glass wool
Glass wool has low thermal conductivity and traps air, making it a good thermal insulator.
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A metal rod transfers heat mainly by what mechanism?
C · Conduction
Heat transfer in solids, especially metals, occurs mainly by conduction through free electrons and lattice vibrations.
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The thermal conductivity of a material is a measure of its ability to
B · Conduct heat
Thermal conductivity quantifies a material's ability to conduct heat.
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In which of the following cases will steady-state conduction be established the fastest through a rod of length L?
B · Rod of high thermal conductivity
A rod with higher thermal conductivity allows faster heat transfer, establishing steady state more quickly.
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The thermal conductivity of a material depends mainly on:
B · Material properties
Thermal conductivity is an intrinsic property depending on the material structure and bonding.
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Refer to the diagram below showing convection currents in a fluid heated at the bottom. What causes the fluid to rise at the bottom and sink at the top?
B · Decrease in fluid density at bottom
Heating decreases fluid density at the bottom, causing it to rise and create convection currents.
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Convection currents are caused primarily because of:
A · Temperature differences causing density changes
Temperature differences cause density variations in fluids leading to upward or downward motion, creating convection currents.
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In which medium does natural convection occur most effectively?
D · Gases
Natural convection is more pronounced in gases due to their lower density and viscosity compared to liquids, while solids do not allow fluid motion.
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For cooling a hot object by airflow, increasing the velocity of air increases heat transfer by increasing
C · Convective heat transfer coefficient
Higher air velocity increases the convective heat transfer coefficient, enhancing convection cooling rates.
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Which of the following is the primary mechanism of heat transfer from the Sun to the Earth?
C · Radiation
Heat from the Sun reaches the Earth primarily by radiation through the vacuum of space.
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Which color surface emits and absorbs thermal radiation most efficiently?
B · Black matte surface
Black matte surfaces have high emissivity and absorb/emit thermal radiation efficiently.
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Refer to the diagram below showing radiation emission patterns from a hot object. Which property of the surface affects the intensity and pattern of emitted radiation?
B · Emissivity
Emissivity determines how efficiently a surface emits thermal radiation; higher emissivity results in more emission.
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Which law quantitatively describes the power radiated per unit area of a black body?
B · Stefan-Boltzmann Law
The Stefan-Boltzmann law describes power radiated by a black body in terms of its temperature.
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Which of these surfaces will have the lowest emissivity and hence radiate the least heat?
A · Polished silver finish
Polished silver reflects most radiation with very low emissivity and thus radiates minimal heat.
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The rate of heat transfer \(Q\) through a rod is directly proportional to thermal conductivity \(k\) and inversely proportional to its length \(L\). Which expression represents \(Q\)?
A · \( Q=\frac{k \Delta T}{L} \)
According to Fourier's law, \( Q=\frac{k A \Delta T}{L} \). Ignoring area, heat flow is proportional to \( \frac{k \Delta T}{L} \).
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Which of the following materials would be most suitable as a thermal insulator in a hot climate building?
C · Polystyrene foam
Polystyrene foam has very low thermal conductivity and is widely used as a thermal insulator.
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Which factors should be considered to minimize heat loss through windows in cold weather?
A · Use double glazing and low-emissivity coatings
Double glazing traps air layers preventing conduction; low-emissivity coatings reduce radiation heat loss.
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Compare heat transfer rates in metals and gases primarily because metals have
A · More free electrons which carry heat
Metals conduct heat well due to free electrons transferring energy faster than molecular vibration in gases.
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For a metal rod of length \(L\) and cross-sectional area \(A\), doubling \(A\) and halving \(L\) affects heat conduction rate by a factor of:
C · 4 times
Heat conduction rate \(Q \propto \frac{A}{L}\). Doubling \(A\) and halving \(L\) multiplies rate by \(2 \times 2 = 4\).
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Which characteristic mostly determines heat transfer differences between solids, liquids, and gases?
A · Thermal conductivity
Thermal conductivity varies for solids, liquids, and gases, influencing the heat transfer rate.
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Heat transfer through gases is slower than through solids mainly because:
B · Gases have lower thermal conductivity
Gases have low thermal conductivity due to wide separation of molecules and lack of free electrons, making heat conduction slow.
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Newton’s law of cooling states that the rate of cooling of a body is proportional to:
B · Temperature difference between body and surroundings
Newton’s law of cooling states heat loss rate is proportional to temperature difference between object and ambient.
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Refer to the graph below showing temperature \(T\) of a hot object over time cooling in ambient temperature \(T_{a}\). What does the curve represent according to Newton’s law of cooling?
A · Temperature decreasing exponentially towards \(T_a\)
Newton’s law predicts temperature falls exponentially towards ambient temperature.
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Which factor does NOT affect the rate of heat loss according to Newton’s law of cooling?
D · Mass of the object
Mass affects thermal capacity but not directly the cooling rate per Newton’s law, which depends on surface area and temperature difference.
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If the cooling constant in Newton’s law of cooling for a body doubles, what happens to the time constant of cooling?
B · It halves
Time constant is inversely proportional to the cooling constant; doubling cooling constant halves time constant.
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Which of the following is NOT a common practical application of heat transfer concepts?
C · Radio transmission
Radio transmission involves electromagnetic waves for communication, not heat transfer.
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Which property is exploited in double glazing windows to reduce heat transfer?
B · Reduced convection by trapping air between panes
Trapped air between panes reduces convection and conduction, lowering heat transfer.
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Which factor most influences the efficiency of a heat exchanger used in industry?
A · Surface area for heat transfer
Larger surface area improves heat exchanger efficiency by enhancing heat transfer.
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Heat transfer rate can be increased by increasing:
A · Temperature difference
Greater temperature difference increases driving force for heat flow, increasing rate.
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Which of the following does NOT affect the rate of conduction heat transfer through a material?
C · Material density
Density does not directly affect conduction rate; thermal conductivity, temperature gradient and area do.
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Which of the following increases the convective heat transfer coefficient in a fluid?
B · Increasing fluid velocity
Increasing fluid velocity enhances mixing and hence the convective heat transfer coefficient.
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Which of the following is NOT a mode of heat transfer?
C · Diffusion
Heat transfer occurs via conduction, convection, and radiation. Diffusion is a mass transfer process, not related to heat transfer modes.
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Which mode of heat transfer mainly occurs in gases and liquids due to bulk movement of fluid?
B · Convection
Convection involves heat transfer due to the bulk movement of fluids like liquids and gases.
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In vacuum, heat transfer occurs predominantly by which mode?
C · Radiation
Since conduction and convection require matter, radiation is the only mode of heat transfer that can occur in a vacuum.
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Heat transfer by conduction in a solid depends primarily on which property?
A · Thermal conductivity
Thermal conductivity is the material property that governs heat transfer through conduction.
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The rate of heat conduction through a metal rod is 100 W. If the cross-sectional area is doubled and the length is halved, the new rate of heat conduction is approximately:
D · 400 W
Heat conduction rate \( Q = \frac{k A \Delta T}{L} \). Doubling area (\( A \)) and halving length (\( L \)) increases \( Q \) by factor 4.
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Which of the following materials is best for reducing heat loss by conduction in building insulation?
C · Glass wool
Glass wool has very low thermal conductivity and is a good insulator to reduce conduction heat loss.
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Refer to the diagram showing convection currents in a heated liquid. What primarily causes the upward movement of the fluid?
D · Decrease in density
Heating decreases the density of fluid locally, causing it to rise due to buoyancy forces, producing convection currents.
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Which factor does NOT affect the rate of heat transfer by convection?
D · Color of the surface
Color affects radiation, not convection. Convection depends on temperature difference, surface area, and fluid thermal properties.
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In natural convection, what primarily drives the fluid motion?
B · Density differences due to temperature variations
Natural convection occurs when density differences caused by temperature gradients induce fluid movement.
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Refer to the diagram of a convection current in a heated fluid inside a container. Which region shows the coolest fluid?
B · At the top surface away from heat source
Cooler fluid sinks and is found at the top surface away from the heat source where it loses heat.
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Radiation heat transfer is the transfer of energy through:
C · Electromagnetic waves
Radiation transfers heat via electromagnetic waves without a medium.
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Which of the following surfaces is the best emitter and absorber of radiant heat?
B · Black matte surface
Black matte surfaces have high emissivity and absorptivity for radiant heat transfer.
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Which statement correctly describes Stefan-Boltzmann law?
B · Heat radiated is proportional to \( T^4 \) of absolute temperature
The Stefan-Boltzmann law states total radiation emitted by a blackbody is proportional to the fourth power of absolute temperature \( (T^4) \).
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Refer to the diagram below showing electromagnetic radiation emitted by a hot surface at temperature \( T \). Which curve best represents the spectral intensity for higher temperature under same area conditions?
B · Curve peaks at shorter wavelength, higher intensity
According to Wien’s displacement law, peak wavelength decreases and intensity increases with higher temperature.
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An astronaut on the moon's surface relies on which mode of heat transfer to keep warm inside the spacecraft?
C · Radiation
In the vacuum of space, radiation is the only mode of heat transfer available.
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Which device uses the principle of heat transfer by radiation for measuring temperature?
B · Infrared thermometer
Infrared thermometers measure temperature by detecting infrared radiation emitted by objects.
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Heat sinks used in electronics predominantly transfer heat by which mode?
B · Convection and Conduction
Heat sinks conduct heat away from components and dissipate it to surroundings mainly by convection.
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Refer to the diagram below showing a double glazing window used to reduce heat loss. Which of the following best explains how the window reduces heat transfer?
A · Eliminates convection by using a vacuum between panes
The vacuum or trapped air between panes reduces convection and conduction, reducing heat loss.
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Which of the following kitchen appliances employs convection for heating food?
C · Convection oven
Convection ovens use fans to circulate hot air, heating food more evenly by convection.
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The efficiency of a solar cooker, an application of radiation heat transfer, can be increased by:
A · Using reflective mirrors to concentrate sunlight
Reflective mirrors focus solar radiation, increasing the cooker temperature and efficiency.
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The working principle of a thermos flask depends mainly on:
B · Preventing convection currents using vacuum and reducing radiation
Thermos flask minimizes heat loss by preventing convection via vacuum and limiting radiation by reflective coatings.
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Which type of heat transfer equation is used to solve most quantitative heat conduction problems?
A · Fourier’s Law
Fourier’s law relates heat conduction rate to thermal gradient and conductivity.
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In the formula \( Q = -k A \frac{\Delta T}{L} \), the negative sign indicates that heat flows:
B · Opposite to the temperature gradient
The negative sign indicates the direction of heat flow is opposite to the temperature gradient (from hot to cold).
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A brass rod of length 2 m and cross-sectional area 0.5 cm² has a thermal conductivity of 109 W/m·K. What is the heat transfer rate if the temperature difference across it is 40 K?
D · 436 W
Using \( Q = k A \frac{\Delta T}{L} = 109 \times 0.5 \times 10^{-4} \times \frac{40}{2} = 436 \text{ W} \).
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Heat transfer by convection from a flat plate is governed by Newton’s law of cooling stated as \( Q = h A (T_s - T_\infty) \). The term \( h \) is called:
B · Convective heat transfer coefficient
\( h \) represents the convective heat transfer coefficient relating heat transfer to temperature difference.
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The emissivity of a surface affects which of the following?
C · Rate of heat radiation emission and absorption
Emissivity indicates how effectively a surface emits or absorbs radiant heat.
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Which of the following equations estimates heat loss by radiation from a surface with emissivity \( e \), surface area \( A \), at temperature \( T_s \) radiating to surroundings at \( T_\infty \)?
A · \( Q = e \sigma A (T_s^4 - T_\infty^4) \)
The Stefan-Boltzmann law for radiation heat transfer incorporates emissivity and the fourth power of absolute temperatures.
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Refer to the diagram below of a heat exchanger. Heat is transferred between two flowing fluids separated by a metal wall. Which modes of heat transfer are involved in this process?
A · Conduction and convection
Heat exchangers transfer heat from hot fluid to cold fluid by convection on both sides and conduction through the separating metal wall.
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The heat transfer rate through a plane wall is 200 W when temperature difference is 50 K. If the temperature difference becomes 100 K, what is the new heat transfer rate assuming all other factors constant?
C · 400 W
Heat transfer by conduction is directly proportional to the temperature difference.
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An object absorbs heat radiation at a rate given by \( Q_1 \) and loses via radiation at rate \( Q_2 \). The net heat change is zero when:
C · \( Q_1 = Q_2 \)
When absorption equals emission, the object is in thermal equilibrium with its surroundings.
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Refer to the diagram showing heat transfer modes: conduction, convection, and radiation between two surfaces at different temperatures. Which mode is represented by wavy arrows?
C · Radiation
Wavy arrows typically illustrate radiation heat transfer via electromagnetic waves.
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The time rate of heat transfer by conduction through a rod is 75 W. If the rod is replaced by another having twice the thermal conductivity and same dimensions, what is the new heat transfer rate?
C · 150 W
Heat transfer rate is directly proportional to thermal conductivity. Doubling \( k \) doubles \( Q \).
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The heat transfer due to convection depends on which of the following properties of fluid?
B · Specific heat and velocity of fluid
Convective heat transfer depends on specific heat capacity and velocity of the fluid since these affect heat transport by bulk motion.
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Reflective coating on building windows primarily reduces heat transfer by:
C · Radiation
Reflective coatings reduce heat transfer by reflecting infrared radiation, thereby lowering radiation heat loss or gain.
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A cup of hot coffee cools faster when uncovered due to which mode(s) of heat transfer?
C · Convection and radiation
Heat is lost by natural convection from the surface as well as radiation to surroundings when the coffee is uncovered.
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If the emissivity of a surface doubles, the rate of heat radiated \( Q \) will, assuming constant temperature, approximately:
A · Double
Heat radiated by a surface is directly proportional to its emissivity \( e \) as per Stefan-Boltzmann law.
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Which of the following statements correctly describes the particle theory of light?
B · Light consists of tiny particles called photons that travel in straight lines.
The particle theory of light states that light is made up of tiny particles called photons that travel in straight lines, explaining phenomena like reflection and photoelectric effect.
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Which experiment is considered primary evidence supporting the wave nature of light?
B · Newton's rings
Newton's rings is an interference pattern demonstrating wave properties of light such as interference and diffraction.
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Refer to the diagram below depicting reflection of light on a plane mirror.
What is the angle of reflection if the incident ray makes an angle of 30° with the mirror surface?
B · 60°
Angle of incidence and angle of reflection are measured from the normal. Angle of incidence = 90° - 30° = 60°, so angle of reflection = 60°.
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If a ray of light strikes a plane mirror at an angle of 40° to the normal, what is the angle between the incident ray and reflected ray?
B · 80°
Angle of reflection equals angle of incidence = 40°. The angle between incident and reflected rays is 40° + 40° = 80°.
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A concave mirror produces an image 20 cm in front of the mirror when the object is placed 30 cm in front of it. What is the focal length of the mirror? (Use mirror formula \( \frac{1}{f} = \frac{1}{v} + \frac{1}{u} \))
C · 15 cm
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Refer to the diagram below showing refraction of light from air into water.
What is the approximate refracted angle if the incident angle is 45° and refractive indices are \( n_{air} = 1.0 \), \( n_{water} = 1.33 \)?
A · 32°
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Which of the following correctly describes the phenomenon of refraction?
A · Bending of light when it passes from one medium to another due to change in speed.
Refraction occurs when light bends due to change in speed as it moves between different media.
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A ray passes from air into a glass slab of refractive index 1.5. If the incident angle is 30°, what will be the angle of refraction inside the glass? (Use Snell’s law \( n_1 \sin \theta_1 = n_2 \sin \theta_2 \))
A · 19.5°
Using Snell's law, \( 1.0 \times \sin 30° = 1.5 \times \sin \theta_2 \Rightarrow \sin \theta_2 = \frac{0.5}{1.5} = 0.333 \Rightarrow \theta_2 = 19.5° \).
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Refer to the ray diagram below showing image formation by a convex lens.
What type of image is formed when the object is placed beyond 2F (twice the focal length)?
B · Real, inverted, diminished
When an object is beyond 2F of a convex lens, a real, inverted, and diminished image is formed between F and 2F on the opposite side.
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What type of lens is used to correct myopia (nearsightedness)?
B · Concave lens
Myopia is corrected using a concave lens which diverges light rays before they enter the eye, helping focus images properly on the retina.
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Refer to the schematic of the human eye below.
Which part of the eye controls the amount of light entering and focuses the image on the retina?
C · Lens
The lens changes shape to focus the light on the retina; iris controls the amount of light but does not focus the image.
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Which of the following vision defects is caused by the eye lens losing its elasticity with age, making near objects appear blurry?
C · Presbyopia
Presbyopia is the inability to focus on near objects caused by loss of lens elasticity due to aging.

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