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!

How far will the box slide?

  1. May 27, 2015 #1
    1. The problem statement, all variables and given/known data
    How far will a box slide if its initial velocity is 1.5 m/s, kinetic friction is 0.15 and the object is 30 kg

    2. Relevant equations
    a= (kinetic friction)(acceleration due to gravity) and
    V(final)^2 - V(initial)^2 = 2(a)(D)

    3. The attempt at a solution
    a= 0.15 x 9.81 m/s^2
    = -1.47 m/s^2 (negative since it is slowing down)

    D= V(final)^2 - V(initial)^2 / 2a
    = 0 - (1.5 m/s)^2 / 2(-1.47 m/s^2)
    = -2.25 m/s^2 / -2.94 m/s^2
    = 0.76 m

    did i do everything right? seems to me like it should go a little further given the value of friction...
     
  2. jcsd
  3. May 27, 2015 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Looks good to me!
     
  4. May 27, 2015 #3

    Doc Al

    User Avatar

    Staff: Mentor

    You solved it using kinematics, which is perfectly fine. What other approach might you have used?
     
  5. May 27, 2015 #4
    Id say id be able to use kinetic energy to solve it, yay or nay?
     
  6. May 27, 2015 #5

    Doc Al

    User Avatar

    Staff: Mentor

    Yes, you could use energy methods to solve this. Good!

    (Try setting it up enough to convince yourself that you get the same equation in the end.)
     
  7. May 28, 2015 #6
    ok so lets say i use energy. I have this equation
    v(initial)^2 = 2(mu)(g)(delta r)

    and i rearrange to find r
    r= v(initial)^2 / 2(mu)(g)

    I put all my numbers in and i get a different answer, 0.54 meters. what did i do wrong?
     
  8. May 28, 2015 #7

    Doc Al

    User Avatar

    Staff: Mentor

    Looks good. Note that this is exactly the same equation you ended up with when you solved it using kinematics.

    Check your arithmetic.
     
  9. May 28, 2015 #8
    ahhh. forgot to square the initial velocity. Thanks for all your help!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted