I believe it's diffraction because it can be nothing else except this ;)
Answer:

Explanation:
According to Gauss's Law, the electric flux of a charged sphere is the electric field multiplied by the area of the spherical surface:

This is identical to the electric flux of a point charge located in the center of the sphere.

Explanation:
Momentum of the system is a constant when there aren't external forces..
So,When first Balls velocity is went down to zero... its momentum is also zero and beacause momentum should be a constant...now second ball must have a momentum of 20 kg * m/s
Zero, cause the positive and negative work cancel out :)