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!

Moments question

  1. Dec 20, 2015 #1
    1. The problem statement, all variables and given/known data
    A metre stick is pivoted at 50cm and is in equilibrium.
    There is a 2.0N upwards force at the 5.0cm mark, and a 12N downwards force at the 40cm mark. Force F acts at the 75cm mark. Find force F. Assume the upwards direction is positive.

    2. Relevant equations
    3. The attempt at a solution

    The leftmost upwards force: 2 x 0.45 = 0.9 Nm (as the force would be 45cm from the pivot)
    The leftmost downwards force: 12 x 0.1 = 1.2 Nm
    Resultant leftmost force: 0.9 - 1.2 = -0.3 Nm

    Force F acts 0.15 m from the pivot, therefore: F x 0.15 m = 0.3 Nm. (resultant would be positive in order to counterbalance).
    Rearranging for F, 0.3/0.15 = 2 N. The programme marks this as incorrect.
     
  2. jcsd
  3. Dec 20, 2015 #2
    See anything strange going on there?
     
  4. Dec 20, 2015 #3
    Nope. The stick is pivoted at 0.5m. If the force acts at the 0.75m mark, it is acting 0.15m away from the pivot.

    EDIT: Ugh, I'm an idiot. Thanks!
     
  5. Dec 20, 2015 #4
    Haha, when I saw your reply earlier without the edit, I was like, "huh"? xD
     
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: Moments question
  1. Moments question! (Replies: 25)

  2. Moments question (Replies: 2)

  3. Moments question (Replies: 7)

  4. Question on moment (Replies: 12)

Loading...