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: Statics Question involving forces and moments

  1. Sep 29, 2008 #1
    Just figured I'd throw this up here. I was able to solve for the reaction at E when a=2 but when I tried for a=7.5, I wound up with something completely different. I was wondering what I'm not incorporating into the steps to solving this.

    Also, it says determine the reactions at A and E. The page got cut when I scanned it.
     

    Attached Files:

  2. jcsd
  3. Sep 29, 2008 #2
    This is my work for solving part a) when a=2

    Sum of the Moment about A = 20(2)-16(1.5)+[5.5(sin(30))+2(cos(30)]E

    -8=[5.5(sin(30))+2(cos(30)]E

    E= -8/[5.5(sin(30))+2(cos(30)] or 3.57 lbs at a 60 degree angle, which is what the book says.

    Now how come when I plug in 7.5 in a, I can't come up with 21.0 lbs? Suggestions would be appreciated
     
  4. Sep 30, 2008 #3

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    what happened to the 32 in-lb couple?
    correct answer (specify direction), wrong equation and math.
    maybe you forgot the 32 inch pound couple?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook