gravity and force?

Question

A 7.0 kg block is pushed 3.0 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 Figure http://www.webassign.net/sf/p5_70.gif . If the coefficient of kinetic friction between block and wall is 0.30, determine the work done by each of the following.

Find
a. the force F

b. gravity

c. the normal force between block and wall

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

Answer 1

a. W=F s sin(30) by definition

mg + f=Fsin(30)
F=(mg + f)/sin(30)
f=uFcos(30)
F=(mg + u Fcos(30))/sin(30)
F(sin(30) - u cos(30)) = mg
F=mg/(sin(30) - u cos(30))

W= F s sin(30)=
W=[ mg/(sin(30) - u cos(30))] s sin(30)=
W=mg s sin(30)/(sin(30) - u cos(30))

b. W=mgS

c.
W=fs=u N s
f= u F cos (30)

d. see b.