Answer
See explanation.
Work Step by Step
The total energy is $\gamma mc^2$.
a. Solve for v when $\gamma=\frac{1}{\sqrt{1-v^{2}/c^{2}}}=4.00$
$$v=c\sqrt{1-1/\gamma^2}=0.968c$$
The relativistic kinetic energy is $(\gamma-1)mc^2$.
$$KE=(4.00-1) (1.67\times10^{-27}kg) (3.00\times10^8m/s)^2$$
$$KE=4.51\times10^{-10}J$$
b.
$$p=\gamma mv=4 (1.67\times10^{-27}kg)(0.968)(3.00\times10^8m/s)$$
$$p=1.94\times10^{-18}kg \cdot m/s$$
c. Already solved, 0.968c.
