1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Tension Question?

  1. Sep 6, 2008 #1
    Two steel wires P and Q have lengths l and 2l respectively and cross sectional areas A and A/2 respectively. Both wires obey Hooke's Law.

    What is the ratio (tension in P/tension in Q) when both wires are stretched to the same extension?
  2. jcsd
  3. Sep 7, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You must show an attempt at solving this before we can help you (forum rules).
  4. Sep 7, 2008 #3
    Yeah, I got it but it's not the right answer...
  5. Sep 7, 2008 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If you post your attempt, perhaps we could help you out.
  6. Sep 7, 2008 #5
    F/A divided by Difference in L/L


    Thus Fl/A(Difference in L)

    L is doubled

    Area is halved
    hence in Q it should be 4
    while in P it is 1

    But the answer says that it is 4:1
  7. Sep 7, 2008 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    That's a good attempt, you're very close.

    Stress/Strain must be the same for both wires, since that is Young's Modulus for the material.

    As you said, (L/A) is a factor of 4 larger for Q.

    What must F be for wire Q, in order that the ratio
    F L/(A ΔL)
    be the same for both wires?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Tension Question Date
Quick Question about Torque and Tension Jan 19, 2018
Question regarding tension Jan 29, 2017
A Question on surface tension Nov 17, 2016
Question about Centripetal Force May 22, 2016