# Equilibrim problems

1. Oct 16, 2009

### gnarrr

http://img27.imageshack.us/img27/8011/physicsproblems.png [Broken]

Last edited by a moderator: May 4, 2017
2. Oct 16, 2009

### rl.bhat

Hi gnarrr, welcome to PF.
Please go through the rules of the PF.
Don't post the problems alone. Show your attempts. List the relevant equations. Still if you don't get, we will help you.

3. Oct 16, 2009

### gnarrr

The first one

1. The problem statement, all variables and given/known data

Consider the bar to have negligible mass. How far from point 'A' must a downward force of 40.5 N be applied in order to achieve rotational equilibrium.

2. Relevant equations
T1=T2
F=0

3. The attempt at a solution

5x9.8x2.1 + 3.5x9.8x4.3 + 40.5xd = 0
d=6.18m

4. Oct 16, 2009

### gnarrr

i figured out the second one

5. Oct 16, 2009

### rl.bhat

First on is wrong.
If you want to take the moment about the fulcrum, you have to consider clockwise and counterclockwise moments and use proper sings.
If you want to take the moments about A, 40.5 N and 3.5 kg produce clockwise moment and the reaction due to all the forces on the fulcrum will produce the counterclockwise moment. Equate them to get d.