609 Pinned to the Wall

When we see the bodies pinned against the wall, it is tempting to imagine that there are some centrifugal forces pushing those people outward against the wall. But there is none. The motion is fully explained by the presence of a centripetal force, not a centrifugal force. The following video will explain.

In the next video, you can see the same principle being applied by these stuntmen. The key  to ride 90-degree rotated on a drum. The key to pulling off this stunt successfully is to ride at a high speed. This forces the bike and wall to be pressed hard into each other, resulting in a large normal contact force. A large normal contact force is crucial because the amount of friction depends on it. It is the frictional force that holds up the weight of the car.



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