Our physics teacher rolls a giant ball down a ramp at the same time also rolls down a plastic car with four wheels. Why is it that the car reaches the bottom first???
As both the ball and the car roll down the incline their potential energy is converted into kinetic energy. There are two forms of kinetic energy, linear and rotational kinetic energy. The linear kinetic energy gain determines how soon they reach the bottom of the incline. Now for the ball, all of its mass is involved in the rotation, while only the wheels rotate for the car. Hence a larger fraction of the total kinetic energy is tied up in rotation for the ball than the car. That is why the car reaches the bottom sooner.