A 10-m uniform beam of weight 100 N is supported by two ropes at the 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?

Question

A 10-m uniform beam of weight 100 N is supported by two ropes at the 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?

anonymous · Answer

I got 700 N.  But this is a review sheet and there is no way to check answer. Is this correct?

anonymous · Answer

I think you need to revise your strategy. I'm not getting 700 N for this. More like 370 N.

anonymous · Answer

yea that makes more sense lol even just reading it 700 N would be way too high.

anonymous · Answer

Yea, focus on the fact that the strings each bear the weight on each of their respective halves of the beam. 

So in this case, the left string bears 50N due to the beam.

Then you have the person sitting on the left side of the beam. Since he is 2m from the left edge, he is 2/10, or 1/5 of the way from the left. This means that he is 80% a part of the left string's bearing.
400 x 0.8 = 320N

Summing the beam and the person's weight that the left string must hold:
50 + 320 = 370 N

anonymous · Answer

yea I got that. I realized I was doing 2 things wrong. First I double the distance and mad only half the length 10 m.  Then I was taking everything at 500 N.  Instead of one point at 400 N and the other at 100 N