So I had a problem today which I couldn't make any sense of. I don't have access to it at the moment but this is a pretty accurate approximation.
Basically, a mass (m) is swinging horizontally on a surface in uniform circular motion. It is attached to a central point by a string of given length (r). The string is exerting a given tension force (T). The period is essentially given as it can be derived from other given values. The question is, what is the force of friction the mass experiences.
So we had some lively debate on the matter amongst my classmates and couldn't come to a satisfactory consensus (especially since none of us are particularly good or knowledgeable at physics). It basically boiled down to the following:
- Friction is tangential to the circle and opposite the direction of the velocity; the tension force is at an angle as a result (to balance out friction with a component)
- Friction is in the same direction as tension (ie. radial, inwards toward the centre) and supplements it as a centripetal force
We also couldn't figure out if the friction in question is static or kinetic. By comparison with a car making a turn, it would be static friction, whereas it was also argued that the mass was sliding, in which case it would have been kinetic (? I'm really unsure about the arguments here).
I'm not altogether too sure of the validity of anything above, as we sort of just speculated based on one or two examples we did in class that weren't too clear themselves. If someone could please explain how to solve this problem (in preferably simple terms because high school), it'd be much appreciated.