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!

How do I calculate mass of pulley and force of friction on AtwoodMach.

  1. Feb 16, 2014 #1
    1. The problem statement, all variables and given/known data
    Basically, I need to calculate the mass of the pulley and friction using data that I collected.


    2. Relevant equations
    I was given: (m1 - m2)g = (m1 + m2 + mp)a + f


    3. The attempt at a solution

    For the first part, I collected data using a sensor to find the acceleration. I kept the total mass attached to each cup on each side of the machine constant but changed the difference in their masses by 10g each run.

    After 6 runs, I plotted my data of Fnet vs Acceleration. Fnet is (m1 - m2)g (I converted g into dynes). When I get my slope, the lab manual says that i should "expect our plot of (m1 - m2)g vs a to have a slope larger than (m1 - m2)g by an amount equal to the effective mass of the pulley mp and a positive intercept equal to the frictional force f"

    My equation turned out to be y = 143.28x + 323.24 (i used best fit line).

    This means 143.28 = m1 + m2 + mp
    In which case mp= 28.5g right?

    Then the force of friction should = 323.4 right?
    Is the unit in dynes?


    For part b, did the same procedure but kept the net force constant instead of the total mass. I gathered my data and plotted

    1/a vs m1 + m2

    I got y = 0.0002x + 0.0059 as my best fit line

    Now I have to use this equation to find the force of friction

    1/a = ((m1 + m2) )/((m1-m2)g-f) + mp/((m1-m2)g-f)


    But i get 4950 which I believe is in Netwons and that would be too much considering 323 dynes = 0.00323 newtons
     

    Attached Files:

  2. jcsd
  3. Feb 16, 2014 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    You seem to be working the equations correctly - they may be the wrong equations of course, so you should check that you understand them. Don't just assume they are right: check!

    The first thing you need to do is check those units - do that by dimensional analysis.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: How do I calculate mass of pulley and force of friction on AtwoodMach.
Loading...