Mechanics (1 Viewer)

[swagswagyoloswag]

A particle P is undergoing uniform circular motion, while being pulled by two strings, one connected at A with the other string connected at B, vertically under A. At A, there is a hollow ring that is suspended.

I drew the tensions in string AP, one tension going away from B towards P and one going away from P towards B, both labelled as T1. There is also another tension (T2) going from P towards A.
The angle between AB and BP, AP are both theta.

My question is, what are the F_net components for the hollow ring?
I did:
F_net vertical = mg = T1costheta
However, my teacher said there is also a horizontal vector (N)
She wrote F_net horizontal = N = T1sintheta
But why is there a force of N?
THe ring is stationary in the horizontal plane, so F_net horizontal = 0? But if that's the case then T1sintheta = 0 ==> theta = 0??

 

[porcupinetree]

Unless you misread your teacher's writing, she should have written:

F_net horizontal = 0
--> T1sintheta - N = 0 (where N is the horizontal normal force of the rod AB on the ring [assuming that rod AB exists; you didn't specify it, but the fact that there's a ring involved strongly suggests it)
--> N = T1sintheta

 

[swagswagyoloswag]

why is there a horizontal force of N? Is it because the ring touches and pulls against the rod so the rod has to have an opposing force?

 

[leehuan]

If one surface touches another, consequently exerting a force on it, there is always a normal reaction force against it from the surface. That is essentially one application of Newton's Third Law of Motion.