You herd your flock of sheep from sea level up to the top of a 100 m cliff. Your

Question

You herd your flock of sheep from sea level up to the top of a 100 m cliff. Your lightest sheep is 100 kg and your heaviest is 250 kg.

(A) What is the amount of work for your lightest & heaviest sheep to make the climb?

(B) If you push your lightest sheep off the cliff, how fast will it be traveling when it hits the ground below and what is its kinetic energy at impact?

(C) If you do the same with your heaviest sheep, what will its speed and kinetic energy be at impact?

(D) What can you say about the work to climb up and the kinetic energy released?

v = vo + at

y = yo + vot + (1/2)at2

Wnet= PEG = PEG-final-PEGinitial

Explanation / Answer

A)

Here , work done = mgh

for lighest sheep ,

Work(lightest) = 100 * 100 * 9.8

Work(lightest) = 98000 J

WOrk(heaviest) = 100 * 250 * 9.8

WOrk(heaviest) = 245000 J

B)

NOw , the velocity at bottom

v = sqrt(2*9.8 * 100)

v = 44.27 m/s

the speed of lighest sheep is 44.27 J

KE = work done

Kinetic energy is 98000 J

C)

v = sqrt(2*9.8 * 100)

v = 44.27 m/s

the speed of heaviest sheep is 44.27 J

KE = work done

Kinetic energy is 245000 J

D)

Here , work done to climb and Kinetic energy are same

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