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

Torque/Vertical Force Problem

  1. Mar 19, 2007 #1
    1. The problem statement, all variables and given/known data
    A 75.0 kg horizontal beam is supported at each end. A 275 kg piano rests a quarter of the way from one end. What is the vertical force on the support closest to the piano?
    What is the vertical force on the support farthest from the piano?

    2. Relevant equations

    3. The attempt at a solution
    I tried using Tcw=Tccw
    so Fpiano*r1+Fbeam*r2=Fbeam*r3
    so 275*9.81*3/4+75*9.81*1/2=Fb*1
    So I got 2391N for the farthest beam
    and 275*9.81*1/4+75*9.81*1/2=Fb*1
    and got 1042N for the closer one but they seem to be wrong...
    can you guys help me on this?

    nvm... I got the answer now I did it backwards so the one with 1042N is farthest and 2391N is the closest...
    thanks lol
    Last edited: Mar 19, 2007
  2. jcsd
  3. Mar 19, 2007 #2


    User Avatar
    Homework Helper

    Simplify your notation. Let A be the reaction force at the support closer to the piano (let's say, the left one), and B the other reaction force. Then set the sum of moments around support B (the one further from the piano) equal to zero. Let the length of the beam be L.

    Edit: don't forget to count the weight of the beam (whose resultant is acting at the center of the beam) in your calculation.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook