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I am trying to understand all the forces on a person in a rotor ride appearing in the homework problem here.

It appear that the the normal force (due to contact between person and rotor's inner surface) provides the centripetal force. It is slightly difficult to visualize that there will be such a strong normal force (as the person is not standing on wall just touching it). Can someone please explain?

Further, if the rotor was not rotating, although the person would fall down, you still have normal force. But when it starts rotating at certain speed (dependent on static friction) the person doesn't fall. The normal force hasn't changed now. What really changed from not moving to moving of rotor that person doesn't fall? Can someone please explain?

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  • $\begingroup$ The inertia of the person has changed! $\endgroup$
    – Jdeep
    May 27, 2020 at 12:36
  • $\begingroup$ The person does not slide down the wall because of friction. $F=\mu N$, and you have explained that there is a normal force $N$. That force of course gets larger the faster the rotor spins. $\endgroup$
    – Peter
    May 27, 2020 at 12:55
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    $\begingroup$ It's currently unclear what exactly this question is asking without clicking on the link you provided. To make questions more accessible and guard against link rot, please include all relevant information, such as the explanation of notation or specific terminology used, in your question. $\endgroup$
    – ACuriousMind ♦
    May 27, 2020 at 14:32

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  1. Although difficult to visualize, Newton's laws show us that the normal force indeed provides the centripetal force required for the circular motion of the person inside the rotor ride.
  2. If the rotor is not rotating, the person would not fall down since they would use their legs to cancel the vertically downward weight acting on them. However, when the ride reaches a particular angular speed, they may take their feet off the ground since the weight would then be counter acted by the static friction of the rotor's inner surface on their back. The change after beginning of rotation is that the person is pressed against this surface once the corresponding centrifugal force pushes them against it and makes the frictional force possible due to this.
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