Question

A ball with a mass of `7 kg` moving at `3 m/s` hits a still ball with a mass of `18 kg`. If the first ball stops moving, how fast is the second ball moving? How much heat energy was lost 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 3+18 xx 0 = 7 xx 0 + 18 xx v`

`21=18v`

`v=21/18`

`v= 1.16m/s`

Loss in kinetic energy = KE_i - KE_f#

Loss in kinetic energy = `1/2 xx 7xx 3- 1/2 xx 18 xx 1.16xx1.16`

Loss in kinetic energy = `10.5 - 12.11`

Loss in kinetic energy = `1.61` Joule