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 Problem with weights

  1. Jun 4, 2010 #1
    1. The problem statement, all variables and given/known data
    A series of weights connected by very light cords are given an upward acceleration of 4.00 m/s2 by a pull P, as shown in Fig. 5.3.( a verticle strand of 4 balls with mass 5,10,15,and 20 kg with the pull at the top) A, B, and C are the tensions in the connecting cords.
    the pull P is closest to:

    290 N
    690 N
    50 N
    200 N
    490 N

    2. Relevant equations
    F= ma

    3. The attempt at a solution
    treating the weights as one mass
    = 552
    Which is not one of the answers. What is the error in my logic?
  2. jcsd
  3. Jun 4, 2010 #2


    User Avatar
    Homework Helper
    Gold Member

    I'm don't see an error in your logic (if I'm interpreting your description of the figure correctly). :approve: Maybe there's an error in your calculations? :uhh: What did you use for m and g?

    [Edit: In other words, your equations seem fine. But I don't know why you ended up with 552]
  4. Jun 4, 2010 #3
    added the masses wrong xD Thank you.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook