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: Determine the coefficient of friction

  1. Feb 23, 2010 #1
    1. The problem statement, all variables and given/known data
    A small 10kg cardboard box is thrown across a level floor. It slides a distance of 6.0m, stopping in 2.2s. Determine the coefficient of friction between the box and the floor.


    2. Relevant equations
    [tex]\[\Delta d={{v}_{0}}t+\frac{1}{2}a{{t}^{2}}\][/tex]
    [tex]\[{{F}_{net}}=ma\][/tex]


    3. The attempt at a solution
    [tex]\[ma=-\mu mg\][/tex]
    [tex]\[10a=-\mu 10(9.8)\][/tex]

    [tex]\[6={{v}_{0}}(2.2)-\frac{1}{2}a{{(2.2)}^{2}}\][/tex]

    How would I go about finding the acceleration?
    The answer given is 0.26, which means the initially velocity of the cardboard box is zero. Is it okay to assume that the box is initially going at zero velocity and then decelerates to zero velocity due to friction?
     
  2. jcsd
  3. Feb 24, 2010 #2

    radou

    User Avatar
    Homework Helper

    Write down the equation for the velocity of the box. What can you conclude from it? Since the box is thrown, obviously the initial velocity can't be zero.
     
  4. Feb 24, 2010 #3
    One more equation to use is vf = vi+at, thus,
    -vi = at
    since vf = 0.
    Now there are two equation with two unknowns (when considering the equations you have posed). You may now solve for acceleration.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook