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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.
Solution
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 .
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