1. The problem statement, all variables and given/known data A person running in a race has to pick up a mass equal to her own mass. Assuming she can still do the same amount of work, her speed will be changed by a factor of a. 0.25 b. 0.50 c. 0.71 d. 1 e. 2 2. Relevant equations E=1/2mv2 3. The attempt at a solution Since m is doubled, v2 should be halved. I'm stuck now. But the correct answer is 0.71. Can someone explain how?