Tension Strongman problem from Physics

  • #1
havechanged
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Tension "Strongman" problem from Physics!

This is the question:
When the strongman suspends the 10 lbs telephone book with the rope held vertically, the tension in each strand of the rope is 5 lbs. If the strongman could suspend the book from the strands pulled horizontally, the tension in each strand would be how much?

A picture of it is at this website: http://www.physics.uwo.ca/ugrad/p02.../p021_lec12.pdf [Broken] with a picture of a guy holding a textbook.

Any answers? And reasons for the answers?

Thanks!
 
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Answers and Replies

  • #2
HallsofIvy
Science Advisor
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I wasn't able access the website given. Since the telephone book weighs 10 pounds and we are told that the "tension in each strand" is 5 pounds, are we to assume there are 2 strands?

It isn't possible to support the book with strands that are literally horizontal- there would be no vertical component of force.

Assuming that the two ropes make angle θ with the horizontal and have tension T, then the vertical component of force for each strand is T sin(θ)- the two together 2 T sin(θ) and that must be 10 pounds: 2 T sin(θ)= 10 so T= 5/sin(&theta).
 
  • #3
havechanged
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Thanks!

I hope you didn't spend too much time doing that! The answer did turn out to be an uncalculatable amount- it is impossible to make it perfectly straight. My teacher mentioned how power lines are bent down too...
 
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