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Help finding the magnitude of the applied force

  1. Jul 10, 2012 #1
    1. The problem statement, all variables and given/known data
    A block of mass 50 kg is free to slide on a frictionless inclined plane that makes an angle of 20° with respect to horizontal. A force F is applied as shown in the drawing pulling parallel to the incline. As a result, the block accelerates up the plane at 4 m/s2.

    known:
    m= 50 kg
    a= 4 m/s^2
    Angle = 20 degrees


    2. Relevant equations
    F=ma
    Fcos(theta)


    3. The attempt at a solution
    F= 50kg* 4m/s2 = 200 N
    200cos(20)=187.9= F x-direction

    * The explanation shows me F- 167 N = 200N
    F=367N
    But I don't know which equation this comes from or where the 167 comes from.
     
  2. jcsd
  3. Jul 10, 2012 #2
    3. The attempt at a solution
    F= 50kg* 4m/s2 = 200 N
    200cos(20)=187.9= F x-direction
    ............................
    200cos(20)=187.9= F x-direction
    What force is this?
     
  4. Jul 10, 2012 #3
    This was my attempt at finding the applied force..
     
  5. Jul 10, 2012 #4
    Can you tell me why you multiply 200 with Cos(20)?

    If you just put an object on frictionless inclined plane, in which direction the object moves?. What makes it move in that direction?
     
    Last edited: Jul 10, 2012
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