Question

A ball with a mass of `7 kg` moving at `1 m/s` hits a still ball with a mass of `10 kg`. If the first ball stops moving, how fast is the second ball moving? How much kinetic energy was lost as heat in the collision?

Answer 1

By momentum conservation ,

`P_i=P_f`------[where `P= momentum= mass xx velocity`]

Let the velocity of ball with mass 10 kg be 'v'.

`7 xx 1+10 xx 0 = 7 xx 0 + 10 xx v`

`7=10v`

`v=7/10`

`v= 0.7m/s`

Loss in kinetic energy = KE_i - KE_f#

Loss in kinetic energy = `1/2 xx 7xx 1- 1/2 xx 10 xx 0.7xx0.7`

Loss in kinetic energy = `7/2 - 49/20`

Loss in kinetic energy = `21/20` Joule