1. Not finding help here? Sign up for a free 30min 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!

Two pulley system

  1. Apr 11, 2008 #1
    Does the tension in the rope from B to A and from A to C remain the same?
    To determine the value of theta when the system is in equilibrium do I need to calculate the sum of all acting x and y components? If so would B and C be negative and A be positive?
  2. jcsd
  3. Apr 11, 2008 #2

    Shooting Star

    User Avatar
    Homework Helper

    Not in general.

    At a point which is in equilibrium, you always have to equate the sum of all forces along any direction to zero. The same goes for a system in static equilibrium, but considering all the forces at one time may not always turn out to be so fruitful

    In this case, the weight of A is balanced by the resultant of the two tensions, which in turn are equal to the weights of B and C respectively. (The pulleys are assumed to be frictionless, and I've just given you the method of solving the problem.)

    No. (I presume you mean their weights.)
  4. Apr 11, 2008 #3
    if B and C are not negative then what is? something has to be negative otherwise the sum of the system won't be equal to zero.
    do i just use a right triangle to solve for the resultant?
    Last edited: Apr 11, 2008
  5. Apr 11, 2008 #4
    are B and C positive and A negative?
  6. Apr 11, 2008 #5

    Shooting Star

    User Avatar
    Homework Helper

    There are reaction forces on the pulleys, acting upward. That gives your negative.

    I didn't quite understand your 2nd Q. Do you mean how to solve for the forces at where A is hanging from? Break up into horizontal and vertical components, and then equate the sums to zero.
  7. Apr 11, 2008 #6
    does this look right
    so i dont even have to find the resultant tension i just solve for theta?
  8. Apr 12, 2008 #7

    Shooting Star

    User Avatar
    Homework Helper

    That is correct, but you should show the steps how you got there.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Two pulley system
  1. Pulley system (Replies: 0)

  2. System of Pulleys (Replies: 1)