1. Not finding help here? Sign up for a free 30min 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!

Why does tension = -RT

  1. Nov 25, 2014 #1
    1. The problem statement, all variables and given/known data
    This figure shows a uniform disk, with mass M = 2.5 kg
    and radius R = 20 cm, mounted on a fixed horizontal axle.
    A block with mass m = 1.2 kg hangs from a massless cord
    that is wrapped around the rim of the disk.

    Sample problem 10-8 (has picture diagram and detailed solution): http://astro1.panet.utoledo.edu/~mheben/PHYS_2130/Chapter11-1_mh.pdf

    2. Relevant equations
    T – mg = ma
    torque = I α
    -RT ??? = (1/2)MR^2 α
    a = a(subscript t) = α R

    3. The attempt at a solution
    I understand how to do the problem but what I don't understand is how they got -RT. Torque is FrSin(theta) and the sin of 90 degrees is 1 not -1 so I would really appreciate any insight on how they got -RT.
     
  2. jcsd
  3. Nov 25, 2014 #2
    Well, it looks like positive direction is chosen to be up and vector T is pointing down so...
     
  4. Nov 25, 2014 #3
    Ok thanks
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Why does tension = -RT
  1. Why does Fn = mgsinΘ (Replies: 3)

Loading...