A 4.0-kg block is pushed 3.1 m up a vertical wall with constant speed by a const

Question

A 4.0-kg block is pushed 3.1 m up a vertical wall with constant speed by a constant force of magnitude F applied at an angle of

= 30°

with the horizontal, as shown in the figure below. If the coefficient of kinetic friction between block and wall is 0.30, determine the following.

(a) the work done by

J

(b) the work done by the force of gravity
J

(c) the work done by the normal force between block and wall
J

(d) By how much does the gravitational potential energy increase during the block's motion?
J

Explanation / Answer

a)

Fsin theta = friction + mg

Fsintheta = u Fcostheta + mg

F ( sin theta - u costheta ) = mg

F (0.24 ) = mg

F = 163.2 N

b)

Work done by gravity

Wg = -mg (3.1)

Wg = -121.52 J

c)

Wn = 0

d)

increase in potential energy

PE = -Wg

PE = 121.52 J

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