With no friction, you can use the relationship between potential and kinetic energy to predict the speed of the car at the bottom of this hill from its starting height. To do this, start by setting the kinetic and potential energy equations equal to one another: K = 1/2 mv2 (2 is squared) = mgh the height is 75cm mass is 0.05 Kg (5 grams) and gravity is 9.81 m/s squared earths gravity