Physics 9702 · AS & A Level · Equations of motion

Equations of motion — practice question

A ball is projected straight downwards towards the ground and bounces back, as shown in Fig. 2.1. When the ball passes A, its speed is $8.4\,\text{m s}^{-1}$. Point A is $5.0\,\text{m}$ above the ground. The ball strikes the ground and rebounds to B. Assume air resistance is negligible.
(a(i))[2]

Calculate the speed of the ball when it reaches the ground.

(a(ii))[1]

Show that the time taken for the ball to reach the ground is $0.47\,\text{s}$.

(b)[3]

The ball rebounds vertically with speed $4.2\,\text{m s}^{-1}$ as it leaves the ground. The ball remains in contact with the ground for $20\,\text{ms}$. The ball rises to a greatest height $h$. The ball passes A at time $t = 0$. On Fig. 2.2, draw a graph to show how the velocity $v$ of the ball varies with time $t$. Extend the graph until the ball has rebounded from the ground and reaches B.

(c(i).1)[2]

For this motion, calculate the change in kinetic energy.

(c(i).2)[3]

For this motion, calculate the change in gravitational potential energy.

(c(i)1)[2]

The ball has a mass of $0.050\,\text{kg}$. It travels from A and arrives at B after rebounding. For this motion, calculate the change in kinetic energy.

(c(i)2)[3]

The ball has a mass of $0.050\,\text{kg}$. It travels from A and arrives at B after rebounding. For this motion, calculate the change in gravitational potential energy.

(c(ii))[2]

State and explain the total change in energy of the ball for this motion.

Worked solution & mark scheme

This 18-mark question has a full step-by-step worked solution and mark scheme. One marking point: Applies equation $v^2 = u^2 + 2as$

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