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: Atwood with Sliding mass and real pulley

  1. Apr 3, 2017 #1
    1. The problem statement, all variables and given/known data
    Block 1 with mass m1=4.04 kg rests on a very low friction horizontal ledge. This block is attached to a string that passes over a pulley, and the other end of the string is attached to the hanging block 2 of mass m2=2.02 kg, as shown.

    The pulley is a uniform disk of radius 11.85 cm and mass 1.980 kg. Calculate the speed of block 2 after it is released from rest and falls a distance of 1.84 m.

    What is the angular speed of the pulley at the instant when block 2 has fallen a distance of 1.84 m ?

    2. Relevant equations
    Wtot=change in Energy
    KE=1/2 mv^2
    W=integral of force*displacement
    N2L for rotation and translation

    3. The attempt at a solution
    The tension of 2 and 1 on the pulley should be different but the accelerations of the blocks would be the same?
    a=m2*g/(mp/2 +m1+m2)
    WEm2=integral from 0 to 1.84 (T2xdx) = 22.47 J
    WT1m1=integral from 0 to 1.84 (T1xdx) = 22.1467 J
    work energy theorem:

    This is not the correct answer, I'm not sure what I am doing wrong would the energy side of the equation be only kinetic?
  2. jcsd
  3. Apr 3, 2017 #2
    I think the diagram would be helpful. Is the pulley frictionless? Also why would the accelerations be same?
  4. Apr 3, 2017 #3
    m1 and m2 are atached by a string on a pulley so wouldn't their accelerations be the same? Screen Shot 2017-04-03 at 12.21.06 AM.png
  5. Apr 3, 2017 #4
    And all the information we were given is on the question so I'm assuming its not frictionless
  6. Apr 3, 2017 #5
    Correct. I can't really understand what the equations for work you've written, up you can just use conservation of energy to do the problem.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted