Illustration of balls rolling between two ramps, changing colour to show the relationship between gravitational potential energy and kinetic energy. At right, two balls are high up on the ramp (blue) and they have high potential energy due to gravity pulling them down towards the floor. As the balls roll down the ramp, their potential energy is converted into kinetic energy and their speed increases (purple). As they hit the floor, the balls are travelling at their maximum speed and their kinetic energy is at a maximum (red). One ball then rolls up the second ramp, and gravity slows it down, converting its kinetic energy to potential energy (blue) again. The other ball continues at constant speed (red) along the flat ground.