Force and Motion — Practice

Question 1

The displacement of a particle after half a circle of radius r is ____.

Accepted Answer

2r (the diameter).

Question 2

A boy on a merry-go-round moving with constant speed is in ____.

Accepted Answer

accelerated motion (the direction, and so the velocity, keeps changing).

Question 3

Velocity is measured in ____ and acceleration in ____.

Accepted Answer

metre/second; metre/second².

Question 4

A body's velocity rises from 4 m/s to 20 m/s in 8 s. Find the acceleration.

Accepted Answer

(20 − 4) ÷ 8 = 2 m/s² (positive acceleration).

Question 5

Why is an object in uniform circular motion said to be accelerating?

Accepted Answer

Because its direction of motion keeps changing, so its velocity changes even though its speed stays constant.

Question 6

A train covers 240 km in 4 hours. Find its speed.

Accepted Answer

60 km/h.

Practice — Force and Motion