What Is the Tension in the Left Rope When a Person Sits on a Supported Beam?

[future_vet]

Homework Statement

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:

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!

 

[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!

 

[future_vet]

-6 sounds like a good answer?

 

[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*.

 

[yone.ultimate]

ya i think you are right