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!

Homework Help: Finding coeffiecient of friction

  1. Feb 10, 2015 #1
    1. The problem statement, all variables and given/known data
    You give a 2.85kg book an initial shove at 2.98m/s and it comes to rest after sliding 3.80m across the floor.
    Find the coefficient of friction between book and floor.

    2. Relevant equations
    3. The attempt at a solution
  2. jcsd
  3. Feb 10, 2015 #2


    User Avatar

    Staff: Mentor

    I think you'll need to explain your attempt. What were you trying to accomplish?
  4. Feb 10, 2015 #3
    i tried solving for a in order to use f=ma
  5. Feb 10, 2015 #4


    User Avatar

    Staff: Mentor

    First, verify that your relevant equation is written correctly and not missing any constants.

    Next, I don't see where in your attempt you accounted for squaring the initial speed. You don't seem to have applied the relevant equation.
  6. Feb 11, 2015 #5
  7. Feb 11, 2015 #6
    I did with conservation of energy. By equating kinetic energy to the frictional work done,


    Where m is mass
    v is initial velocity
    mu is coefficient of friction
    N is normal force i.e. mg
    d is distance travelled

    I got an answer, mu = 0.16
  8. Feb 11, 2015 #7


    User Avatar
    Science Advisor

    Going another route, I arrived at the same expression. But - I seem to have a slightly different answer: μ≈0.12.
  9. Feb 11, 2015 #8
    That could be possible because of certain approximations in the calculation, like value of "g", or something else, i guess.
  10. Feb 11, 2015 #9


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    No, 0.16 looks too inaccurate for that. Note that the mass is irrelevant.
    But more seriously, you are not supposed to present something so much more Like a complete solution than the original poster has yet managed. Gneill's post is the right sort of hint.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted