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!

Mass-spring system with friction

  1. Dec 5, 2008 #1
    A mass M slides across a horizontal table. It collides with a spring, compresses the spring, and then the mass-spring system rebounds. This system can be used to find the spring constant k. When the mass first hits the spring at x = 0, it has speed v0.

    a.) Let the coefficient of kinetic friction be μk. Assume that the spring plus mass compresses to a distance l, rebounds, and stops when it returns to x = 0, having compressed the spring only once. Use the work-energy relation, Wnon-cons = ΔPE + ΔKE to find the required coefficient of friction μk in terms of l, v0 and g.

    b.) Next, consider just half the cycle, with the mass starting out with speed v0 at position x = 0, and stopping (for an instant) at x = l. Use the work-energy relation once again to find a relation between k, l, v0, μk, and g.

    c.) Use the results of parts (a) and (b) to solve for the spring constant k in terms of v0, μk, and g.
     
  2. jcsd
  3. Dec 5, 2008 #2

    LowlyPion

    User Avatar
    Homework Helper

    How would you think to go about solving it other than putting it here for someone else to solve?
     
  4. Dec 5, 2008 #3

    CompuChip

    User Avatar
    Science Advisor
    Homework Helper

    Yes, very interesting.
    Any ideas? Formulas you might be able to use?
     
  5. Dec 5, 2008 #4
    Well i know that KE is equal to 1/mv^2 and the potential energy of a spring is equal to 1/2kl^2. The work done by friction is going to be equal to μkmgl
     
  6. Dec 5, 2008 #5

    LowlyPion

    User Avatar
    Homework Helper

    Won't the work done by friction be 2*μk*m*g*l ? (Twice the distance - to compression and back to equilibrium.)

    So maybe add it all up and solve for μk?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?