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: Blocks on a Turntable

  1. Sep 21, 2008 #1
    Two identical blocks are tied together with a string and placed along the same radius of a turntable that is spinning about its center. The inner block is 4 cm from the center and the outer block is 5 cm from the center. The coefficient of static friction between the turntable and the blocks is ┬Ás = 0.74, and the string is taut.

    a) What is the maximum angular frequency such that neither block slides?
    I got w= 12.7 which was right

    b) Now suppose that the blocks each have a mass m = 21 g. For the value of w you just found, what is the tension in the string?
    T= ?N

    I am stuck on b) I have 2 eqns:
    T+[tex]\mu[/tex]mg=mR1w^2
    -T+[tex]\mu[/tex]mg=mR2w^2

    So I keep getting 17N each time I try. What am i doing wrong?
    T=mR1w^2-[tex]\mu[/tex]mg
    =21x.05x12.7^2 - .74x21x9.81
    =169.4-152.4= 17N

    Help Please!
     
  2. jcsd
  3. Sep 22, 2008 #2
    I can't help you dude. I need help with the same problem. All I can figure out is that the net force points to the center of the circle I believe, and https://www.physicsforums.com/latex_images/18/1883140-2.png [Broken] probably doesn't point toward the center, I think.

    I'm still stuck on A and have no idea how to procede.
    If you finish the problem, and if you have some extra time could you help me with it please? :)
     
    Last edited by a moderator: May 3, 2017
  4. Sep 22, 2008 #3
    did u convert grams to kg?
     
  5. Sep 22, 2008 #4
    I was actually just doing that as when i saw i got a new reply. I thought i tried that before but i must have miscalculated. i got it right now thanks!
     
  6. Sep 22, 2008 #5
    haha yeah, i just solved it thanks to some help from someone else. peace. :)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook