Question

A 5.3-kg block is pushed 2.3 m up a vertical wall with constant speed by a constant force of magnitude F applied at an angle of θ = 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 F
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


im getting wrong answer for 1) i got 216.2 J but that is incorrect
2) im also getting wrong when i plug in everything.
3) is 0
4) is 119.50

so can u please look at 1 and 2 and help me

Answer 1

a) F sin30= mg + Ff
so we need to find Ff
Fn = F cos30 = Ff/mu
so Ff = mu F cos30
substitute
F sin30 = mg + mu F cos30
solve for F
F sin30 d = W
b) W = mgh = 5.3*9.8*2.3 (same as d)
c) Normal force can NEVER do work

Answer 2

Late, I know, but

b] W = -mgh, not mgh. Ran into this problem myself. :/