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 F required pushing a box at angle (theta) for constant v

  1. Oct 17, 2011 #1
    1. The problem statement, all variables and given/known data

    a crate with mass m rests on a horizontal floor. a woman pushes down at an angle of theta below the horizontalon the frace with a force F, the coefficient of kinetic friction is Uk.
    a) what magnitude of force F is required to keep the crate moving at a constant velocity?

    2. Relevant equations

    Ff(frictional force)=UkFn

    Constant velocity which means Fnet=0

    3. The attempt at a solution

    since Fnet is 0 you can set horizontal force = to frictional force

    Uk(mg + Fcos(theta))=Fsin(theta)
    (Uk(mg+ Fcos(theta))/sin theta = F

    This is apparently not right and i cant thing of what else to do -_- help would be very much appreciated as well as an easier way of approaching problems with only symbols.
    Last edited: Oct 17, 2011
  2. jcsd
  3. Oct 17, 2011 #2
    You are very close, but I think you mixed up the components of F. I think your cos and sin should be switched.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook