Assume that the small-massed particle is
and the heavier mass particle is
.
Now, by momentum conservation and energy conservation:


Now, there are 2 solutions but, one of them is useless to this question's main point so I excluded that point. Ask me in the comments if you want the excluded solution too.

So now, we see that
and
. So therefore, the smaller mass recoils out.
Hope this helps you!
Bye!
I need more details like r u reading from something
Answer:
The electric potential at the surface of a charged conductor<u> is always such that the potential is zero at all points inside the conductor.</u>
Explanation:
Each point on the surface of a balanced charged conductor has the same electrical potential.
The surface on any charged conductor in electrostatic equilibrium is an equipotential surface. Since the electric field is equal to zero inside the conductor, the electric potential at any point inside and on the surface is equivalent to its value.