PHYSICS  PLEASE HELP
posted by Anonymous .
A box of weight w=2.0 N accelerates down a rough plane that is inclined at an angle 30 degrees above the horizontal. The normal force acting on the box has a magnitude n= 1.7 N, the coefficient of kinetic friction between the box and the plane is .30, and the displacement d of the box is 1.8 m down the inclined plane.
A)What is the work W done on the box by the weight of the box?

W=m•g•h=m•gvdvsin30

W=m•g•h=m•g•d•sin30

What is the work Wn done on the box by the normal force?

A box with weight w = 900 N is on a rough surface, inclined at an angle of 37 degrees. The box is kept from sliding down (in equilibrium) by means of an external force F. The other forces acting on the box are the normal and friction forces, denoted by n and f. A force diagram, showing the four forces which act on the box, is shown in Figure 4.3. The magnitude of f is 150 N. The external force F is removed and the box accelerates. The magnitudes of the other forces are unchanged. The acceleration of the box is closest to: