# Static Equilibrium and tension

1. Apr 13, 2007

### future_vet

1. The problem statement, all variables and given/known data
A 10-m uniform beam of weight 100 N is supported by two ropes at its ends. If a 400 N person sits at 2.0 m from the left end of the beam, what is the tension in the left rope?

I thought the answer would be:
3. The attempt at a solution
100*5 + 400*7 = T*10
3300 = T*10

T = 330 N

But it's not correct. What am I doing wrong?

Also:
A book weighs 6 N. When held at rest above your head the net force on the book is? I say -6 N. Is this correct?

Thanks!

2. Apr 13, 2007

### future_vet

Ah simple math error. It's 370.
Any feedback for the other question? I have another topic about the same subject that is actually more urgent. Thanks!

3. Apr 13, 2007

### future_vet

-6 sounds like a good answer?

4. Apr 13, 2007

### e(ho0n3

The force exerted by your head on the book is 6 N. I would not call this the net force though. The net force on the book is 0 because it is *at rest*.

5. Jan 17, 2009

### yone.ultimate

ya i think you are right