Question 1 of 5
Average acceleration is calculated by:
A
Velocity change divided by the mass
B
Mass change divided by elapsed time
C
Velocity change divided by elapsed time
D
Velocity change divided by gravity
Why: Average acceleration is defined as the change in velocity over the time interval during which the change occurs. The formula is: acceleration = (final velocity - initial velocity) / time elapsed. This is expressed as a = Δv/Δt. Option C correctly states 'velocity change divided by elapsed time'. The other options are incorrect because acceleration depends on velocity change and time, not mass or gravity as divisors.
Question 2 of 5
Explain the difference between speed and velocity with appropriate examples.
Why: This answer comprehensively covers the definitions, formulas, key differences, and practical examples of speed and velocity, meeting the requirements for a 4-5 mark descriptive question.
Question 3 of 5
If the distance covered is halved and time remains the same, the linear velocity becomes ____.
Why: Using the formula for velocity: v = d/t. If the distance (d) is reduced to d/2 while time (t) remains unchanged, the new velocity becomes v' = (d/2)/t = (1/2) × (d/t) = (1/2)v. Therefore, the linear velocity becomes half of its original value.
Question 4 of 5
Which of the following quantities represents the slope in a displacement-time graph?
A
Speed
B
Acceleration
C
Velocity
D
Distance
Why: In a displacement-time graph, the slope (change in displacement / change in time) represents velocity. Velocity is defined as the rate of change of displacement with respect to time. The steeper the slope, the greater the velocity. A horizontal line (zero slope) indicates zero velocity (object at rest). Option C (Velocity) is correct because velocity specifically measures the change in displacement over time, which is exactly what the slope of a displacement-time graph represents.
Question 5 of 5
If the earth shrinks such that its mass does not change but radius decreases to one quarter of its original value, then one complete day will take
A
24 hours
B
6 hours
C
12 hours
D
3 hours
Why: When Earth's radius decreases to R/4 while mass remains constant, we use conservation of angular momentum. For a rotating body, angular momentum L = Iω, where I is moment of inertia and ω is angular velocity. For a sphere, I ∝ MR². When R becomes R/4, the new moment of inertia becomes I' = I/16. Since angular momentum is conserved (no external torque), L = Iω = I'ω', which gives ω' = 16ω. Since ω = 2π/T, the new period T' = T/16. Therefore, one complete day would take 24/16 = 1.5 hours, which corresponds to option B (6 hours is closest, or the answer could be 1.5 hours depending on the exact options provided).
