1. The problem statement, all variables and given/known data An oxygen atom is four times as massive as a helium atom. In an experiment, a helium atom and an oxygen atom have the same kinetic energy. What is the ratio vHe /vO of their speeds? 2. Relevant equations K=.5mv2 3. The attempt at a solution .5mHe(vHe)2=.5(4mHe)(vO)2 I'm not sure what to do with that though, how to solve for the ratio.