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!

Motion of the System (Pulley)

  1. Oct 14, 2011 #1
    1. The problem statement, all variables and given/known data
    I'm currently doing a lab that focuses on a pulley and have got stuck on on part.

    The goal here is to use the data from the Atwood’s pulley experiment to test the validity of (m1-m2)g=(m1+m2+1/R^2)a. In this equation, take the quantity (m1−m2)g as the y variable and the acceleration a as the x variable. This makes the equation linear. What does the slope and the y-intercept correspond to in this equation?

    Regarding the y-intercept, it is expected to be zero according the equation. However, you will probably get a non-zero value for the y-intercept! What could be the reasons behind this deviation? Did we miss something while deriving the equation? Include a clear argument regarding this issue in your lab report.

    2. Relevant equations
    (m1-m2)g=(m1+m2+1/R^2)a
    y=mx+b


    3. The attempt at a solution
    I honestly don't see what they are really asking in this situation. By looking at the equation as though it fits y=mx+b, the slope would be (m1+m2+1/R^2) however I am unsure as to what that is supposed to imply.
     
  2. jcsd
  3. Oct 14, 2011 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    What is R?

    ehild
     
  4. Oct 14, 2011 #3
    R is the radius (2.25 cm).
     
  5. Oct 14, 2011 #4

    ehild

    User Avatar
    Homework Helper
    Gold Member

    Your equation (m1-m2)g=(m1+m2+1/R^2)a is wrong. You can not add cm-2 to kg. How did you get that equation?


    ehild
     
  6. Oct 14, 2011 #5
    ahhh sorry I misread. R is radians but I don't have radians given.
     
  7. Oct 15, 2011 #6

    ehild

    User Avatar
    Homework Helper
    Gold Member

    R is not radians, either. It is the radius of the pulley, but the correct formula is

    (m1-m2)g=(m1+m2+I/R^2)a,

    where I is the moment of inertia of the pulley.

    This formula does not take friction into account. Because of friction, the system does not start to move when (m1-m2)g is less than the force of friction.


    ehild
     
  8. Oct 15, 2011 #7
    Oh thank you! That makes much more sense. I'm still really confused about how it relates to the slope and y-intercept though.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Motion of the System (Pulley)
  1. Pulley System (Replies: 3)

  2. Pulley system (Replies: 3)

  3. Pulley systems (Replies: 9)

Loading...