A force of constant magnitude pushes a box up a vertical surface as shown in the

Question

A force of constant magnitude pushes a box up a vertical surface as shown in the figure. The box moves at a constant speed. If the mass of the box is 5.40 kg, it is pushed 2.80 m vertically upward, the coefficient of friction is 0.350 and the angle e is 30.0°, determine the following. (a) work done on the box by 752.578 X A force diagram will help you determine the magnitude of the force F acting on the box. Can you write an expression for the work done by the force F in terms of the magnitude of the force, the distance the force acts and the angle between the direction of the force and the displacement vector? (b) work done on the box by the force of gravity (c) work done on the box by the normal force (d) increase in gravitational potential energy of the box as it moves up the wall Additional Materials eBook

Explanation / Answer

a) net force = F sin theta - m g - (F cos theta * 0.35)

0 = F * sin 30 - (5.40 * 9.8) -( F * cos30 * 0.35)

F (0.5 - (cos 30 * 0.35)) - 52.92 = 0

F = 268.7 N

work done on the box F = 268.7 * sin 30 * 2.80

Wbox = 376 J

b) work done on the box by the force of gravity = -5.4 * 9.8 * 2.8

= -148.2 J

c) work done on the box by the normal force = 0 J

d) increase in gravitational potential energy of the box as it moves up the wall = 5.4 * 9.8 * 2.8

= 148.2 J

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