Problem 2 A Bookmark this page 2.mu 1 point possible (graded, results hidden) 2)

Question

Problem 2 A Bookmark this page 2.mu 1 point possible (graded, results hidden) 2) During a contest, competitors have to drag a log for 15 m across a horizontal floor by pulling horizontally with an attached rope. Under the same conditions (mass and coefficient of friction), competitor A moves the log at 3.6 km/h competitor B at 10.8 km/h, and competitor C at a speed increasing at a constant acceleration from 10.8 km/h to 144 km/h. Rank the work done by the pulling force Wp. on the log in each case.

Explanation / Answer

Work done by the pulling Force is W = chnage in kinetic energy

for A

since he was pulling with constant speed then change in kineti energy is zero

hence Wp,A= 0 J

similarly Wp,B = 0 J

but Wp,C = 0.5*m*(V^2 - Vo^2) = 0.5*m*(14.4^2 - 10.8^2)*(5/18)^2 = 3.5 m

so the answer is

Wp,A = Wp,B < Wp,C

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