1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    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!

Tensile force in elevator problem

  1. Sep 28, 2012 #1
    1. The problem statement, all variables and given/known data
    Two blocks, each of mass m are hung from the ceiling of an elevator as in the figure below. The elevator has an upward acceleration a. The strings have negligible mass.

    http://imageshack.us/a/img856/2241/5p031.gif [Broken]

    Find the tensions T1 and T2 in terms of m, a, and g.

    Which string would break first if a was sufficient large?

    What are the tensions if the cable supporting the elevator breaks?



    2. Relevant equations

    F = ma

    3. The attempt at a solution

    My answers were:

    T1 = 2(ma + mg)
    T2 = ma + mg

    the upper string would break first

    T1 = 2(-ma + mg)
    T2 = -ma + mg

    can anyone please check my work and see if these answers are correct? thanks
     
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Sep 28, 2012 #2

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Looks good for the first part. For the second part, the elevator could no longer be accelerating up, since only gravity firce would be acting down. The elevator and its contents would be in free fall. In free fall, what is the acceleration? Redo your calcs for the tensions.
     
  4. Sep 28, 2012 #3
    So...if the object is in free fall that would mean:

    T1 = 0 and T2 = 0???
     
  5. Sep 28, 2012 #4

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Yes, good.
     
  6. Sep 28, 2012 #5
    Thank you for the help. Makes sense now that i think about it the right way
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Tensile force in elevator problem
Loading...