Speed, acceleration and motion graphs — GCSE Physics practice questions

Question 1

A delivery drone flies from its depot to a house 2.4 km away, to the north-east.

Which quantity describing this flight is a vector?

Accepted Answer

A: displacement. A vector has both magnitude and direction. Displacement is the distance in a stated direction (2.4 km to the north-east), so it is a vector. Distance, speed and kinetic energy have magnitude only, so they are scalars.

Question 2

A juggler throws a ball vertically upwards. Air resistance is negligible and the acceleration of free fall is 9.8 m / s².

Which row describes the velocity and the acceleration of the ball at the instant it reaches its highest point?

Accepted Answer

B: zero · 9.8 m / s² downwards. At the top the ball is momentarily at rest, so its velocity is zero. Its weight still acts, so its acceleration is still 9.8 m / s² downwards: a moment later it is moving downwards.

Question 3

A small probe is released from rest 18 m above the surface of a moon that has no atmosphere.
It hits the surface at a speed of 12 m / s.

What is the acceleration of free fall on this moon?

Accepted Answer

B: 4.0 m / s². The acceleration is constant, so the average speed is ½ × (0 + 12) = 6.0 m / s. The fall takes 18 ÷ 6.0 = 3.0 s. The acceleration is 12 ÷ 3.0 = 4.0 m / s². (The same answer comes from ½ m v² = m g h: g = v² / 2h.)

	velocity	acceleration
A	zero	zero
B	zero	9.8 m / s² downwards
C	9.8 m / s downwards	zero
D	9.8 m / s downwards	9.8 m / s² downwards