Answer
$E=3.63MeV$
Work Step by Step
To find energy, the value of gamma must be known. Do this by using a known value of $\beta=0.990$ to get a gamma value of $$\gamma=\frac{1}{\sqrt{1-\beta^2}}=\frac{1}{\sqrt{1-.990^2}}=7.09$$ Substitute this value into the energy equation $$E=\gamma mc^2$$ along with $m=9.11 \times 10^{-31}kg$ to get an energy of $$E=7.09(9.11 \times 10^{-31}kg)(3.00\times 10^8m/s)^2$$ $$E=5.81\times 10^{-13}J$$ Converting joules to MeV yields $$3.15 \times 10^{-10}J \times \frac{1.00GeV}{1.60\times 10^{-10}J}=3.63 MeV$$
