#### Answer

m=50 kg

#### Work Step by Step

The first step to solving this problem is to multiply both sides by 2, giving you the new equation:
2E=m$v^{2}$
Next, divide both sides by $v^{2}$ to get m by itself, giving you the new equation:
m=$\frac{2E}{v^{2}}$
After this step, plug in the values for E and v given by the problem:
m=$\frac{2(2500)}{10^{2}}$
Lastly, multiply the numerator and then divide by the denominator to give you the answer:
m=50 kg