In order for a body to move with uniform velocity in a circular path, there must exist some force towards the centre of curvature of the circular path. This is centripetal force. By Newton's Third Law, there must exist a reactive force that is equal in magnitude and opposite in direction. This is the reactive centrifugal force.
My question is simple, and it is probably the result of lack of common sense but here it goes:
In uniform circular motion, why don't these forces simply cancel each other out? If they did, how would we know they exist in that situation?
When I swing a rock tied to a rope, I feel the centrifugal force, but not the centripetal force. In this situation how can the reactive force be greater than the force itself?
Best Answer
NO, They do not cancel out each other, while centripetal (center seeking force) is generally provided by some other agency/force, like for revolution of planets it is provided by gravitational force, centrifugal force(outward force) is a pseudo force which is felt in the reference frame of the revolving/rotating body. Clearly since the two forces belong in different frames, they do not cancel out each other in your frame i.e. from the viewers frame they cancel out only in the frame of reference of body as the body does not move in that frame.
When you are rotating a stone/ball tied to a thread you seem to think that you are feeling an outward/centrifugal forcre, but it is actually the tension of the thread, see at the end of the ball tension is directed towards the centre of rotation and is hence centripetal force, but the same tension at the point/centre of rotation is directed towards the ball, therefore you feel an outward force but it is not centrifugal force.