Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How Can I get started on drawing this free body

  1. Jan 24, 2012 #1
    1. The problem statement, all variables and given/known data

    I have way to many unknowns to start the process of solving equations.

    2. Relevant equations

    ƩFx = 0
    ƩFy = W

    3. The attempt at a solution

    I was given the answer of one force being .885W and the other is .201W. The problem is a recommended problem not for a grade but I would like to get a full understanding of these problems
  2. jcsd
  3. Jan 24, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi Ryantruran! Welcome to PF! :smile:

    Hint: the cylinders are smooth, so the forces will all be normal, so they will lie along the lines joining the centres. :wink:
  4. Jan 24, 2012 #3
    does this look like an ok freebody diagram http://imgur.com/ntgFv
  5. Jan 25, 2012 #4


    User Avatar
    Science Advisor
    Homework Helper

    Hi Ryantruran! :smile:

    (just got up :zzz: …)

    Nooo … that's not a free-body diagram at all. :redface:

    A free-body diagram should show all the external forces on a body (or bodies).

    Yours does not show the external forces from the "walls", nor does it show the weights (acting through each centre of mass).

    Also, this is probably one of those questions where you need to draw more than one free-body diagram (you could for example draw one for each cylinder, and one for all three together).

    See the PF Library on "free body diagram" for more details.

    (btw , your diagram is wrong anyway, the bottom cylinders should touch each other, and you've omitted the right-hand "wall")
  6. Feb 5, 2012 #5
    You can solve it with a fbd for C alone. As there are three forces acting on C, it is possible to draw a force triangle to scale and calculate the values using trig.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook