Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Tension Strongman problem from Physics

  1. Oct 13, 2003 #1
    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?

    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Oct 14, 2003 #2


    User Avatar
    Science Advisor

    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).
  4. Oct 14, 2003 #3

    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...
    Last edited: Oct 15, 2003
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook