Help With A,B, and C please Suppose a man with 120 kg mass is stranded at the bo

Question

Help With A,B, and C please

Suppose a man with 120 kg mass is stranded at the bottom of a ravine, 20 meters deep. The rope used to rescue the man also has a mass of 30 kg. a. First, find the work necessary to lift the man out of the ravine under the assumption that the rope has no mass. b. Assuming now the rope does have mass, find the work necessary to lift the dangling rope to the top of the ravine without the man hanging on to it. c. Now find the total work necessary to lift the dangling rope to the top of the ravine with the man hanging on tightly.

Explanation / Answer

A) Work done is W = F*S*cos(theta)

here theta is the angle between Force F and displacemnt S

here theta = 180 degrees

Force F = m*g = 120*9.8

S = 20m

then W = 120*9.8*20*cos(180) = - -23520 J

B) W = F*S*cos(180) = -30*9.8*20 = - -5880 J

C) W = F*S*cos(180) = -(120+30)*9.8*20 = - 29400 J

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