# Homework Help: Mechanics of materials beam Problem

1. Sep 4, 2014

### Chacabucogod

A 1-ton wall hoist consists of a horizontal beam, supported by a tension rod at 30 deg, as shown. The rod is to be designed with a factor of safety 5 with repeat to its yield point of 30,000 PSI. Determine its necessary cross section

S=F/A

30000/5=6000PSI
-2000+Rsin(30)=0
R=4000
R_x=4000cos(30)
6000=4000cos(30)/A

The solution from the book is 2/3 which would imply that the force is 4000. Am I doing something wrong?

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2. Sep 5, 2014

### SteamKing

Staff Emeritus
You've just thrown some numbers down without any explanation or units. It's hard to follow what you are doing.

What is R supposed to be?

It seems like you're supposed to figure out the tension in the tension rod, which apparently is not the same as figuring out the compression load in the horizontal beam. The area 'A' should have some units attached.

3. Sep 5, 2014

### Chacabucogod

Never mind. It's the rod's tension, not the cantilever. Seems like I read it wrong. Thank you