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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

    Ff=Fsin(theta)
    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.
    thanks!
     
    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.
     
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