Question

A ball is dropped from a height of 10 m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back? (g = 10 m s^–2)

Answer 1

Let the mass of the ball be m, then, the initial potential energy of the ball

= mgh = 10 x 10 x m

= 100 m J

Since the energy of the ball reduces by 40% after striking the ground, energy left with the ball = 60% of P.E.

= `60/100 xx 100 "m"`

= 60 m J

Let the ball bounce back to height W due to this remaining energy,

∴ mgh = 60 m

h = `(160"m")/"mg"`

= 6m