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: Finding tension in a rope problem

  1. Feb 28, 2010 #1
    1. The problem statement, all variables and given/known data
    A 60kg man is climbing a rope that is connected to a pulley and on the other side the rope is connected to a 100kg block. what is the tension in the rope?

    2. Relevant equations
    T-mg+F=ma

    3. The attempt at a solution
    this was my attempt:
    Mg-T-F=Ma;
    adding the equations;
    I get a=0.4
    T+F=60(g+a)
    =840N
    but the answer is wrong. where did i go wrong??
     
  2. jcsd
  3. Feb 28, 2010 #2
    What's that extra F doing in there? You have two cases: The block and the climber.

    Draw free body diagrams. There are two forces acting on both the block and the climber. They will both fight against each other to equal the Net force = m*a. Create a system of equations.
     
  4. Feb 28, 2010 #3
    for the man it is:
    T-mg+F=ma
    for the block:
    Mg-T-F=Ma

    is that correct?
     
  5. Feb 28, 2010 #4
    Oh I see what you're doing now.

    Newton's second law states that [tex]F_{net} = m \cdot a[/tex] for the case of a rope problem, the net force IS the combination of tension and weight. Get rid of the extra F in there and you are right.
     
  6. Feb 28, 2010 #5
    ah! got it. thank you so much!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook