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5) A person pulls on a 50 kg desk w/ a 200N force acting at a 30Á angle above the horizontal. The desk does not budge.

AWrite the equation that describes the forces which act in the x-direction.
BWrite the equation that describes the forces which act in the y-direction.
CDetermine the x and y components of the force of tension.
DDetermine the values of the frictional and normal forces.

6) Suppose the person were PUSHING down at a 30Á angle with 200N of force. The desk still does not move.

AWrite the equation that describes the forces which act in the x-direction.
BWrite the equation that describes the forces which act in the y-direction.
CDetermine the values of the frictional and normal forces.

Verified Answer :

syed514

5)
a. The equation that describes the forces which act in the x-direction: 
     Fx = 200 cos 30 

b. The equation which describes the forces which act in the y-direction: 
     Fy = 200 sin 30 

c. The x and y components of the force of tension: 
    Tx = Fx = 200 cos 30  
    Ty = Fy = 200 sin 30 

d.Since desk does not budge, frictional force = Fx
                                                                        = 200 cos 30 

                                                 Normal force = 50 g - Fy
                                                                       = 50 g - 200 * sin 30 
____________________________________________________________
6) Let F_net = 0
a. The equation that describes the forces which act in the x-direction: 
    (200N)cos(30) - F_s = 0

b. The equation that describes the forces which act in the y-direction:
    F_N - (200N)sin(30) - mg = 0

c. The values of friction and normal forces will be:
     Friction force= (200N)cos(30),
     
The Normal force is not 490N in either case...
Case 1 (pulling up)
F_N = mg - (200N)sin(30) = 50g - 100N = 390N

Case 2 (pushing down)
F_N = mg + (200N)sin(30) = 50g + 100N = 590N

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