Kinetic Energy Questions

A bomb of mass $16\text{kg}$ at rest explodes into two pieces of masses $4\text{kg}$ and $12\text{kg}$. The velocity of the $12\text{kg}$ mass is $4\text{m/s}$. The kinetic energy of the other mass is:

Two infinitely large insulating plates are uniformly charged such that the potential difference between them is $V_2-V_1=20\text{V}$. The plates are separated by $d=0.1\text{m}$. An electron is released from rest on the inner surface of plate 1. What is its speed when it hits plate 2? ($e=1.6\times 10^{-19}\text{C}$, $m_e=9.11\times 10^{-31}\text{kg}$)