# 1002 Gravitron

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. Those people are moving in circles, which required a centripetal force. The normal contact force that the wall exerted on the bodies provided this required centripetal force.

The motion is fully explained by the presence of a centripetal force, not a centrifugal force.

When we see the people struggling to move towards the centre of the spinning drum, we are again tempted to think that some centrifugal forces are flinging them outward towards the wall. Wrong again. What’s happening is that when those people leave the wall, they can only count on the friction on their shoes to provide the required centripetal force. Their shoes obviously did not provide enough friction, hence they were not able to keep up with the circular motion of the spinning drum. They thus moved in a somewhat tangential direction, and ended up looking as if they were moving along the radius of the spinning drum.

Again, the motion is fully explained by the insufficient or absence of a centripetal force. Let’s banish the centrifugal force forever.