Question

a body strikes with floor with a velocity of u ms and rebounds with same speed find the change in the speed

Answer 1

Ok...change in velocity means..

initial velocity - final velocity

as velocity is vector means it has both magnitude and direction...let's take initial velocity direction as positive..

so change will be = U - (-U) = 2U

As rebounding velocity will be in opposite direction to the initial velocity... that's why we take -ve U in the place of final velocity
..

Thanks