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# Starting from rest, a 4.80-kg block slides 2.00 m down a rough 30.0° incline. The coefficient of kinetic friction between the block and the ?

Starting from rest, a 4.80-kg block slides 2.00 m down a rough 30.0° incline. The coefficient of kinetic friction between the block and the incline is

μk = 0.436.

(a) Determine the work done by the force of gravity.

J

(b) Determine the work done by the friction force between block and incline.

J

(c) Determine the work done by the normal force.

J

(d) Qualitatively, how would the answers change if a shorter ramp at a steeper angle were used to span the same vertical height?

### 1 Answer

- oubaasLv 72 months ago
(a)

Determine the work W done by the force of gravity

W = m*g*h = m*g*L*sin 30° = 4.8*9.80*2*0.5 = 47.0 joule

(b)

Determine the work W' done by the friction force between block and incline

W' = m*g*cos 30°*μk *L = 4.80*9.80*0.866*0.436*2 = 35.5 joule

(c)

Determine the work W'' done by the normal force

Normal force N = m*g*cos 30°

W'' = N*h' ...h' being the displacement having the same direction of N

since the block is in contact with the incline, then h' = 0 and W'' = 0

(d)

How would the answers qualitatively change if a shorter ramp at a steeper angle were used to span the same vertical height?

# answer a) : W doesn't change , since h is the same

# answer b) : W' decreases, since both L and cos Θ are smaller

# answer c) : W'' still remains zero