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: Calculating work

  1. Oct 27, 2009 #1
    1. The problem statement, all variables and given/known data
    There is a piano that is being lowered 5 m. It has gravity force acting in y-direction (down) of 2500 N. Then it has two ropes attached, they are vectors that are pointing up and out. so T1 is 1830N [W60[tex]\circ[/tex]N] and T2 is 1295N [E45[tex]\circ[/tex]N]

    2. Relevant equations
    so the work by gravity is 12500 J
    the work by T1 is 4575 J (opposite direction to work by gravity)

    3. The attempt at a solution
    so it would make sense that the work by T2 is somewhere close to 7000 J so that the net work is 0. but when i calculate it i get around 4000 J. Can someone check my math...

    For T2:
    W = Fcos[tex]\theta[/tex][tex]\Delta[/tex]r
    = 1295*cos45*(5)
    = 4579 J

    ???? - thnx!
  2. jcsd
  3. Oct 28, 2009 #2
    Hi there,

    I believe you have a problem with the angle of T1. Becausem, when I verified your calculations, I come to precisely 0 net work.

  4. Oct 28, 2009 #3
    oh yes thank you! i was using an angle that gave the component perpendicular to motion :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook