Turning a Car

Turning a car, or driving a car around a curve, is a very common experience for many people. What is the physics of this event?

First, A Little Review:

car in a turn - top view

The diagram above shows a car (blue rectangle) going around a turn (top view). There must be a centripetal (center-pointing) force on the car.

Acceleration is a vector quantity. So, we know that no matter what else might be going on, a turning car is accelerating - even if its speed is constant - since it is changing direction. This is a centripetal (center-pointing) acceleration. Newton's Second Law says that accelerations are caused by forces, so there must be a force on the car while it is turning. This force is the inward-pointing centripetal force, as shown in the diagram at right. This centripetal force is the net force on the car.

We also know that forces are interactions between objects. Something must be exerting the centripetal force - it doesn't "just happen." What is exerting the centripetal force on the car? Well, it depends on the situation...

last update January 11, 2008 by JL Stanbrough