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: Force clarification

  1. Oct 17, 2005 #1
    I'm just wondering if I'm doing this correctly..

    If I have something like this: http://img326.imageshack.us/my.php?image=pull6cx.png

    It's a closed system where the weights on the cart will get placed on the bottom holder for each trial... To find the 'force of the falling weight' I would take the mass*acceleration, where acceleration is determined by how fast the cart goes in a certain distance right? I wouldn't just take the mass*gravity when it's connected to a pulley like that would I?
  2. jcsd
  3. Oct 17, 2005 #2
    The only forces acting on the falling weight are Fg1 (force of gravity) and FT (force of tension in the rope). For the falling weight alone, Fnet1 = ma = Fg1+FT.

    Since FT is applied in both directions in the rope, it "cancels out" when you involve the entire system. For the entire system, Fnet = (m1+m2)a = Fg1+Ff2.

    Hope that helps.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook