A car is running at a speed of 15 km h^-1 while another similar car is moving at a speed of 45 km h^-1. Find the ratio of their kinetic energies.

A ball of mass 0.5 kg slows down from a speed of 10ms^-1 to that of 6ms^-1. Calculate the change in kinetic energy of the ball.

A body of mass 10 kg is moving with a velocity 20 m s^-1.

If the mass of the body is doubled and its velocity is halved,

find:

(i) the initial kinetic energy, and

(ii) the final kinetic energy.

A truck weighing 1000 kg changes its speed from 36 km/h to 72 km/h in 2 minutes.

Calculate:

(i) the work done by the engine and

(ii) its power.

(g =10 m/ s^-2)