Question

a ball is dropped from a height of 10m. if the eneregy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back? (g=10m/s)

Answer 1

According to the law of conservation of energy,

Potential energy at top is equal to the kinetic energy at the bottom

So, initial kinetic energy = mgh = 10mg

40% of this energy is lost.

So, final kinetic energy = (60/100)x(10mg)

= 6mg

Kinetic energy at the bottom is equal to the potential energy at the top.

Let h be the height upto which ball bounce back,

6mg = mgh

h = 6 m