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!

Pulley system acceleration

  1. Nov 6, 2004 #1
    Hi, I'm working on a project involving a two-weight pulley system. The idea is to take two washers of slightly different masses and devise a method of determining a numerical value for the acceleration of gravity using the pulley. Basically the pulley slows down the effect of gravity, and I need to find that new acceleration.

    mass one = 13.92 g = 0.01392 kg
    mass two = 16.31 g = 0.01631 kg

    I set up five test configurations at different heights, so I have five heights total. Then I released the washers and recorded the time it took to hit the floor with a friend (so three sets of two values). Then I averaged them. So, at this point I have five different hieghts, each with an average time it took to hit the floor. Here are three of them:

    height one = 1.02 m
    time = 1.78 s

    height two = 1.115 m
    time = 1.728 s

    height three = 12.22 m
    time = 1.843

    Now, here is where I'm starting to have doubts. This is an equation I used to find the "slowed down" acceleration.

    gravity * (mass one - mass two) = (mass one + mass two) * acceleration

    This equation doesn't need the time, and I'm REALLY starting to wonder. Using this equation I get an acceleration value of 0.7756 m/s^2. To verify this, I take the first height of 1.02 m and use this derived equation:

    t^2 = (2*height)/acceleration (from h= 1/2at^2)

    Take the square root and you get a value of 1.62 seconds. Height two, I get 1.70 seconds, height three 1.78 seconds. What's wrong here??? Those are NOT the recorded values I have!!

    Another verification is h=1/2at^2

    For the first time (my recorded value and a=0.7756), h = 1.23 m. What is wrong HERE too???

    Basically I am VERY confused. Can someone PLEASE help me out? I need the acceleration of the system using my recorded times and heights. Any help is very much appreciated!
  2. jcsd
  3. Nov 6, 2004 #2
    Just to add a comment here, the pulley system is the two weights on your basic pulley, friction and string weight negligible. Thanks!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Pulley system acceleration