I need help with force/momentum/vectors

  • Thread starter melaku
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  • #1
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I am asked to do this.

"A uniform beam is attached to two springs scales as shown. The scales read 71 lb and 100 lb respectively. Find the wight of the beam."

http://img144.imageshack.us/my.php?image=phy8wq.png


I have no idea how to go on about solving this. please someone explain it to me like you would explain it to a child.

Thanks in advance.
 

Answers and Replies

  • #2
brewnog
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I'm not being awkward, but I don't understand the diagram one bit.
 
  • #3
Meir Achuz
Science Advisor
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My guess is that the diagram is meant to show a rod held up by two strings,
one at 45 degrees with a tensiion of 71#, and the other at 60 degrees from the horizontal with a tension of 100#. This is consistent with their being no net horizontal force on the rod.
The net horizontal force is 100 cos 60 - 71 sin 45=0 (as it should).
The net upward force on the stick is 100 sin 60 + 71 sin 45 =87 + 50 = 137#,
which equals the weight of the stick.
 
  • #4
I reccomended him here for help guys, don't make me look bad:)

That diagram IS funky though
 
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