Question

A ball with a mass of `10 kg` moving at `3 m/s` hits a still ball with a mass of `15 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

`2 \ "m/s"` after the collision.

Explanation:

I'm not sure how to answer the second part of the question, but I can answer the first part.

So, we are going to use the law of conservation of momentum equation, which is

`m_1u_1+m_2u_2=m_1v_1+m_2v_2`

where `m_1,m_2` are the masses of the two objects, `u_1,u_2` are the initial velocities of the two objects, and `v_1,v_2` are the final velocities of the two objects.

So, plugging in the values, we get

`10 \ "kg"*3 \ "m/s"+15 \ "kg"*0 \ "m/s"=10 \ "kg"*0 \ "m/s"+15 \ "kg"*v_2`

`=>30 \ "kg m/s"=15 \ "kg"*v_2`

`v_2=(30color(red)cancelcolor(black)"kg""m/s")/(15color(red)cancelcolor(black)"kg")`

`=2 \ "m/s"`

So, the second ball will move at `2 \ "m/s"` after the collision.