Question

A ball of mass 0.5 kg slows down from a speed of 5m/s^-1 to that of 3m/s^-1. Calculate the change in kinetic energy of the ball.

Answer 1

Mass of ball= 0.5kg

Initial velocity=5m/s

Initial kinetic energy = `1/2 xx "mass" xx ("velocity") ^ 2`

`= 1/2 xx 0.5 xx (5)^2`

`= 1/2 xx 0.5 xx 25 = 6.25 "J"`

Final velocity of the ball =3m/s

Final kinetic energy of the ball =

`1/2 xx "mass" xx ("Velocity")^2`

`=1/2 xx 0.5 xx (3)^2`

`= 1/2 xx 0.5 xx 9 = 2.25  "J"`

Change in the kinetic energy of the ball = 2.25 J - 6.25J = -4J

There is a decrease in the kinetic energy of the ball .