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!

Question on torques. quick one.

  1. May 7, 2016 #1
    1. The problem statement, all variables and given/known data
    Untitled 3.jpg

    2. Relevant equations
    ok, I thought that the torque from the mass 'm' would be equal to torque from mass 'M'

    3. The attempt at a solution
    I wrote down:

    m * g * (d/4) = M * g * d

    (m/4) = M

    m = 4M

    Thus, the ratio is 4M : 1 m, which gives answer 1.

    However, the solutions say that the answer is 5.

    Could anyone please weigh in, and thanks in advance for the help!
     
  2. jcsd
  3. May 7, 2016 #2

    billy_joule

    User Avatar
    Science Advisor

    I agree with your answer.
     
  4. May 7, 2016 #3

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    No, you have shown 4M=1m. Think of M and m as numbers there. What is M/m?
     
  5. May 8, 2016 #4
    ahh 1/4. Right, thanks!
     
  6. May 8, 2016 #5
    I have another method,
    For the system to be in equilibrium the centre of mass should lie exactly on the pivot.

    Assume the pivot to be at (0,0)
    assume M to be at (d,0)
    assume m to be at (-d/4 ,0)
    Applying the formula of center of mass
    x c.o.m. = (m(-d/4) +Md)/(m+M) = 0

    Md = md/4
    M:m=1:4
     
  7. May 8, 2016 #6
    That sir is an awesome and time-saving method! Thanks a lot!!! Everyone 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: Question on torques. quick one.
  1. Quick Torque Question (Replies: 2)

  2. Quick torques question (Replies: 3)

Loading...