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: How much work done by friction when a box w/apparent mass..?

  1. Nov 19, 2016 #1
    1. The problem statement, all variables and given/known data
    How much work is done by friction when a box with an apparent mass of 325kg moves horizontally across a floor with coefficient of friction of .33 and is pulled at 59.9 degree angle for 2.60 m? What is the force that is pulling the box?

    2. Relevant equations
    W=Fdcos@ (@= theta)

    3. The attempt at a solution
    I searched for what apparent mass was, but what I found seemed to do with volume and water displacement, which aren't related to this problem. Instead I tried solving the second question first because I needed Normal force to solve the work done by friction.

    For my free body diagram, I had force applied (Fa) in the y direction upwards on the y axis along with normal force. Along the negative y axis I had weight. Force of friction (Ff) was along the negative x axis, and force applied in the x direction was on the positive x axis.

    In the x direction...
    Ff=Facos@ (since no acceleration)
    uN = FaCos@

    In the y direction...
    Fasin@ + N = W (again since no acceleration)
    N= mg - FaSin@

    So plugging in,,,
    u(mg-Fasin@) = FaCos@

    Solving for Fa I got...
    umg-uFasin@ = Facos@
    Fa= umg/(usin@ + cos@)
    Fa= (.33*325 kg*9.8)/(.33sin59.9+cos59.9)
    Getting that the force applied = 1335.50 N, but this is not correct.

    Any help would be appreciated, thanks in advance.
  2. jcsd
  3. Nov 19, 2016 #2
    I found this on a Google search:
    In physics, apparent weight is a property of objects that corresponds to how heavy an object is. The apparent weight of an object will differ from the weight of an object whenever the force of gravity acting on the object is not balanced by an equal but opposite normal force.
  4. Nov 19, 2016 #3
    If you assume ##apparent \ weight = mg - N## do you see a way to proceed?
  5. Nov 19, 2016 #4
    Yes, thank you!
  6. Nov 20, 2016 #5
    Try taking the apparent weight = N.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted