A 70 kg trunk is pushed 4.2 m atconstant speed up a 30° incline by a constant ho

Question

A 70 kg trunk is pushed 4.2 m atconstant speed up a 30° incline by a constant horizontal force.The coefficient of kinetic friction between the trunk and theincline is 0.15.
Calculate the work done by the applied horizontalforce. Calculate the work done by the weight of the trunk? How much energy was dissipated by the frictionalforce acting on the trunk? From now suppose the 70 kg trunk is pushed 4.2m at constant speed up a 30° incline by a force alongthe plane (not as in the figure). The coefficient of kineticfriction between the trunk and the incline is 0.15.
Calculate the work done by the appliedforce? Calculate the work done by the weight of the trunk.? How much energy was dissipated by the frictionalforce acting on the trunk? A 70 kg trunk is pushed 4.2 m atconstant speed up a 30° incline by a constant horizontal force.The coefficient of kinetic friction between the trunk and theincline is 0.15.
Calculate the work done by the applied horizontalforce. Calculate the work done by the weight of the trunk? How much energy was dissipated by the frictionalforce acting on the trunk? From now suppose the 70 kg trunk is pushed 4.2m at constant speed up a 30° incline by a force alongthe plane (not as in the figure). The coefficient of kineticfriction between the trunk and the incline is 0.15.
Calculate the work done by the appliedforce? Calculate the work done by the weight of the trunk.? How much energy was dissipated by the frictionalforce acting on the trunk?

Explanation / Answer

m = 70 kg, d = 4.2 m, = 30°, = 0.15.
applied force = F, let its direction be angle with theincline, ( = for 1st case, and = 0 for secondcase)
Fcos = mgsin + f
N = mgcos + Fsin
Fcos = mgsin + (mgcos + Fsin)
F = mg(sin + cos)/(cos -sin)

1. = , F = 546 N
Calculate the work done by the applied horizontal force.
F*d*cos = 1987 J

Calculate the work done by the weight of the trunk
mg*d*cos(90 + ) = -1441 J

How much energy was dissipated by the frictionalforce acting on the trunk? (mgcos + Fsin)*d

2. From now suppose the 70 kg trunk is pushed 4.2m at constant speed up a 30° incline by a force alongthe plane (not as in the figure). The coefficient of kineticfriction between the trunk and the incline is 0.15.
= 0, plug vslues.

Calculate the work done by the applied force? Calculate the work done by the weight of the trunk.? How much energy was dissipated by the frictionalforce acting on the trunk?

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