MODEL RELEASED. Measuring stopping distance. Two pupils have released a toy car on a ramp and are measuring its stopping distance compared to the point on the ramp from which they released it. Velocity at the bottom of the ramp will be roughly proportional to the height from which they released the car. Assuming that air resistance is negligible, the stopping distance will then be related to velocity quadratically: assume frictional force is mgR, where R is a constant, kinetic energy is 0.5mv. Work done against kinetic energy is thus mgRd, where d is distance. So putting kinetic energy equal to work done we derive d = (V)/2Rg.