# Static friction between two objects.

1. Mar 26, 2013

### Matt_h

a child (m=30kg) sits 5m from the axis of rotation on a flat turn table which makes a full rotation every 8 seconds.

A. find the childs period (t) and frequency (f)
Full rotation every 8 seconds, T=8
Frequency = inverse of period = 1/8

B. What is the tangential velocity of the child?
Vtan=ωR
w=D(θ)/dt
(2pi/8)*5= 3.926

C. What is the centripetal acceleration of the child? what must the centripetal force acting on the child be?
Acentripetd=v^2/R
3.926^2/5=3.082
F=ma
30*3.082=92.48

D. If this is the fastest the child can go without slipping off the turntable, determine the coefficient of friction between the child and the table surface.

I cant figure out what equation to use.
the only equations i have written down from class are
Fs-maxs*FN
Fkk*FN

Any help would be great

Last edited: Mar 26, 2013
2. Mar 27, 2013

### ehild

Correct.

If you want to keep 4 significant digits, round off properly.

The force of static friction provides the centripetal force for motion along the circle. You are right, the maximum static friction is μsFN.

What is N?

ehild