# Torque on a uniform beam

1. Mar 4, 2009

### Hotsuma

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

Determine the net torque on the 4.5-m-long uniform beam shown in the figure:
http://session.masteringphysics.com/problemAsset/1057865/3/GIANCOLI.ch10.p030.jpg" [Broken]

A) Calculate about point C, the center of mass (CM)

B)Calculate about point P at one end.

2. Relevant equations

$\tau=F*\theta$

3. The attempt at a solution

In this case I have the answers for the values with the same figure, so I know the summation of forces along this pole must be equal to 8.5 N. From there I multiply the length of my bar to get 38 Nm, which is correct. However, I don't know how to get this from the figure. From there, I have no idea how to get the torque around point p.

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

### Delphi51

The formula is not correct. It should be the component of force perpendicular to the rod times the distance from the point.

For the uppermost force, it would be
Torque = 56*sin(30)*4.5/2

3. Mar 4, 2009