Physics 9702 · AS & A Level · Gravitational potential energy and kinetic energy

Gravitational potential energy and kinetic energy — practice question

A resultant force $F$ causes an object of mass $m$ to travel a straight-line distance $s$. This force produces acceleration $a$, changing the speed from initial speed $u$ to final speed $v$.
(a(i).1)[1]

State an equation for the work $W$ done by the force, in terms of $a$, $m$ and $s$.

(a(i).2)[1]

State an equation for the distance $s$, in terms of $a$, $u$ and $v$.

(a(ii))[2]

Use your answers in (i) to show that the kinetic energy of the object is given by $\text{kinetic energy} = \frac{1}{2} \times \text{mass} \times (\text{speed})^2$. Explain how you obtain this result.

(b(i))[2]

For the ball’s motion from X to Y, draw a solid line on Fig. 2.1 to show: 1. the distance moved (label this line D); 2. the displacement (label this line S).

(b(ii))[3]

By considering energy transfer, determine the height $h$ of point Y above the ground.

(b(iii))[2]

On Fig. 2.2, sketch how the kinetic energy of the ball changes with vertical height above the ground as the ball moves from X to Y. No numerical values are required.

(c(i))[2]

For the movement of the ball from X to Y, draw a solid line on Fig. 2.1 to show: 1. the distance moved (label this line D) 2. the displacement (label this line S).

(c(ii))[3]

By considering energy transfer, determine the height $h$ of point Y above the ground.

(c(iii))[2]

On Fig. 2.2, sketch how the ball’s kinetic energy varies with its vertical height above the ground as it moves from X to Y. No numerical values are needed.

Worked solution & mark scheme

This 18-mark question has a full step-by-step worked solution and mark scheme. One marking point: So $W = m a s$

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