# A Uniform Beam Supported by a Cable

1. Jan 21, 2013

### ginza88

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

A uniform 250 kg beam is supported by a cable connected to the ceiling, as shown in the figure. The lower end of the beam rests on a rough, horizontal floor. What is the magnitude of the tension in this cable?

Image of the problem:
http://session.masteringphysics.com/problemAsset/1026378/6/yg.10.70.jpg

2. Relevant equations

Fnet=ma=0

3. The attempt at a solution

I know that this problem is easiest to complete using torques, but I was told to try it without using torque (if possible). That being said, here is my attempt:

http://imgur.com/jKr3tDC

I know that I got the right answer but I am not sure how. Aren't the 40 degrees and the 20 degrees are the wrong angles to use when using a horizontal/vertically oriented plane?

2. Jan 21, 2013

### haruspex

Your working does indeed look wrong.
You show the tension resolving into T cos(20o) horizontally and T sin(20o) vertically, whereas the cable makes an angle 60o to the horizontal.
You don't show any frictional force at the ground, but there must be one.