# Homework Help: Uniform rod resting against rough vertical wall supported by a string.

1. Apr 23, 2014

### kozor

1. The problem statement, all variables and given/known data
Uniform rod AB with end B resting against rough vertical wall. Coefficient of friction between wall and rod is μ.

Rod is 2m long and has mass 3kg.

Rod is kept in limiting equilibrium by a light inextensible string, one end of which is attached to the end A of the rod and the other to point C on the wall 2m above B. Angle ABC=120°.

The end B of the rod is about to slip down the wall.

1. By taking moments about C, show that the normal reaction at B is approx. 12.7N.

2. Find the value of μ.

PS: A labelled diagram would be very helpful! Thanks!

2. Relevant equations
n/a

3. The attempt at a solution

Have been able to sketch what I think are all the forces acting on the rod, but does the normal reaction + friction + T-resolved = downward force of 2g-resolved? Do I take the weight of the rod to act from the centre?

Last edited: Apr 23, 2014
2. Apr 23, 2014

### paisiello2

Yes, it would! Can you provide one?

3. Apr 24, 2014

### kozor

No worries.

http://imageshack.com/a/img836/6874/gykt.png [Broken]

Last edited by a moderator: May 6, 2017
4. Apr 24, 2014

### dauto

Yes, unless otherwise stated, its safe assume the rod is uniform in which case its center of gravity is at the center