Starting from rest, a 4.2-kg blockslides 2.90 m down a rough 30.0°incline. The c

Question

Starting from rest, a 4.2-kg blockslides 2.90 m down a rough 30.0°incline. The coefficient of kinetic friction between the block andthe incline is µk = 0.436. (a) Determine the work done by the force ofgravity.
1 J

(b) Determine the work done by the friction force between block andincline.
2 J

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

(d) Qualitatively, how would the answers change if a shorter rampat steeper angle were used to span the same vertical height?
4 (a) Determine the work done by the force ofgravity.
1 J

(b) Determine the work done by the friction force between block andincline.
2 J

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

(d) Qualitatively, how would the answers change if a shorter rampat steeper angle were used to span the same vertical height?
4

Explanation / Answer

m = 4.2 kg s = 2.90 m = 30 = .436 a) W = (mgsin30)(s) = ((4.2)(9.8)sin30)(2.9) = 59.7 J b) W = (mgcos30)(s) = ((.436)(4.2)(9.8)cos30)(2.9) = 45.1J c) Total work done by normal force W = 0 J because the normal forceand displacement are perpendicular to each other.

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