Wat is the formula of coefficient of static friction if the mass is not given?

Question

i dont know wat formula to use since there is no given mass in the question. and how can i find the force?

im a bit confused..

here's the question:

A coin is placed 11.0cm from the axis of a rotating turntable of variable speed. When the speed of the turntable is slowly increased, the coin remains fixed on the turntable until a rate of 36rpm is reached and the coin slides off. What is the coefficient of static friction between the coin and the turntable?

Answer 1

F=(mue) N

F=force,,N=normal force

F=m V^2 /r

N=mg,,,g=9.81 M/sec^2

.

m v^2 /r =m g (mue)

v^2/r g =(mue)

v=2 pi r (frequency)=2 3.14 r (36/60sec)=6.28 0.6 r

v=3.768 r

.

(mue)=14.34 r/9.81=1.461 r=1.461 (0.11 meters)=

(mue)=0.16  static friction coefficent.

.

Answer 2

Put the force required for centripetal acceleration equal to weight x coefficient of static friction.

You can express both in terms of the mass, m. This will occur on both sides of the equation, so you can cancel it and you don't need to know it.

Principle: the frictional force and the force required for acceleration are both directly proportional to the mass.

Answer 3

Hi,

This is really tough one, Need to take some help from someone,

The best would be if you check it on

http://www.extramarks.com