| The Differential
in this exhibit is like the differential gear used in rear-wheel-drive
cars. It shows that the two rear wheels can turn independently.
In this demonstration, either wheel can be stopped while the other
continues to turn, but both cant be stopped at the same time.
In a rear-wheel-drive car, the power of the engine is used to make
the two rear wheels spin. But when a car turns the corner, the inner
wheel turns more slowly, since it covers a smaller distance than
the outer wheel. Without a differential, the two wheels would be
locked in step with by the turning axle, and one of the wheels would
have to skid as the car went around the corner. Differentials are
not needed in front-wheel-drive cars because the wheels can be pointed
in the direction of the turn.