Question

A ball with a mass of `3 kg` moving at `8 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 kinetic energy was lost as heat in the collision?

Answer 1

Around `1.33 \ "m/s"`.

Explanation:

I can only answer the first part.

We use the law of conservation of momentum, which states that,

`m_1u_1+m_2u_2=m_1v_1+m_2v_2`

• `m_1,m_2` are the masses of the two objects

• `u_1,u_2` are the initial velocities of the two objects

• `v_1,v_2` are the final velocities of the two objects

Plugging in the values, we get,

`3 \ "kg"*8 \ "m/s"+18 \ "kg"*0 \ "m/s"=3 \ "kg"*0 \ "m/s"+18 \ "kg"*v`

`24 \ "kg m/s"+0=0+18 \ "kg"*v`

`v=(24 \ "kg m/s")/(18 \ "kg")`

`=(24color(red)cancelcolor(black)"kg""m/s")/(18color(red)cancelcolor(black)"kg")`

`=1.bar(3) \ "m/s"`

`~~1.33 \ "m/s"`