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!

Homework Help: Issue with an aspect of moments and reactionary force

  1. Mar 24, 2013 #1
    My main issue here is determining the correct reaction force, I'm truly lost as to where I'm making a mistake?
    The question is: A uniform rod of length 2m and mass 5kg is connected to a vertical wall by a smooth hinge at A and a wire CB as shown. If a 10kg mass is attached to D, find:
    The tension in the wire (Obvious, answered on the attachment)
    The magnitude of the reaction in the hinge at A (truly stuck here!)

    Am i correct in assuming the forces are in equilibrium and that the reactionary force would be perpendicular to the wall itself?

    Any assistance/advice would be much appreciated, I have an exam tomorrow based around these concepts. Thanks.

    The attachment is my attempt so far with the desired answer for the second part in red at the bottom:

  2. jcsd
  3. Mar 24, 2013 #2
    Check your value of tension. It seems to be wrong.

    Regarding the normal reaction, the equation using moments seems to yield an answer of 686N but the force equation i.e. to balance the components of force along the length of the rod seems to yield that R=73.5 N, assuming that the rod is at rest. So I guess somewhere ( I don't know where) there's a mistake.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted