1. The problem statement, all variables and given/known data A rocket is propelled vertically upward from the earth which has a radius R0. After its fuel has become exhausted, the rocket reaches its highest point at a height of 2R0 above the surface of the earth and then falls vertically down back to the earth. With what speed does the rocket strike the surface of the earth? Air resistance is negligible. Express in terms of R0 and g at the surface of the earth. Show clearly your reasoning. 2. Relevant equations U=-GMm/R KE=1/2mV2 3. The attempt at a solution So I did everything accordingly, I ΔU + ΔK = ΔE which is 0. So -ΔU = ΔK. But my answer includes mass which the question does not want, what am i doing wrong? Shall I use another formula-relation ?