Question

A ball of mass 0.5 kg slows down from a speed 5m per second to that of 3metre per second calculate the change of its kinetic energy of the ball

Answer 1

Change in kinetic energy = 1/2mv^2 - 1/2 mu^2 = 1/2×5/10 ×3 - 1/2 × 5/10 × 5

= - 0.5J ( negative sign as the ball is slowing down )

Answer 2

K.E = 1/2 m (v^2-u^2)

given:-

m = 0.5 kg

u = 5 m/s

v = 3 m/s

hence,

K.E = 1/2 x 0.5 x [(3)^2 - (5)^2]

     = 1/2 x 0.5 x - 16

     = -  0.5 x 8

     = - 4 J

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