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 to find the coefficient of friction in a rotor-ride?

  1. Nov 4, 2014 #1
    1. The problem statement, all variables and given/known data
    I have no values at all, so it's just going to be the variables in the relevant equations. I need to define mu using those variables.
    A carousel is moving in a circle at velocity v and has a radius r. It is moving fast enough that each person with mass m is pinned against the wall and not moving. What does mu (the coefficient of friction) have to be in order for the people to not move? Define it in terms of m, g, r, or v.
    I know that it has a square root involved somewhere because all the answer choices have square roots.

    2. Relevant equations
    friction=mu(normal force)
    centripetal Force= mv^2/r
    Force of Gravity=gm
    3. The attempt at a solution
    Centripetal force=normal force=force of friction/ mu
    force of friction/ mu=mv^2/r
    force of friction= force of gravity (because friction pushes up with the same amount as gravity pushes down)
    mg/ mu= mv^2/r
    g/ mu =v^2/r
    (cross multiply)
    mu*v^2= gr
    mu=(gr)/(v^2)
    But I know this can't be right because there's no square root.
     
  2. jcsd
  3. Nov 4, 2014 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    Hi b! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    What are the answer choices offered?
     
    Last edited by a moderator: May 7, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted