A 5.00-kg watermelon is dropped from rest from the roof of a 28.0-m -tall buildi

Question

A 5.00-kg watermelon is dropped from rest from the roof of a 28.0-m -tall building and feels no appreciable air resistance. Calculate the work done by gravity on the watermelon during its displacement from the roof to the ground. Just before it strikes the ground, what is the watermelons kinetic energy? Just before it strikes the ground, what is the watermelons speed? Would the answer in part A be different if there were appreciable air resistance? Would the answer in part B Be different if there were appreciable air resistance? Would the answer in part C be different if there were appreciable air resistance?

Explanation / Answer

A) W_gravity = m*g*h

= 5*9.8*28

= 1372 J

B) K = m*g*h (beacuse energy is conserved)

= 1372 J

C) Apply, (1/2)*m*v^2 = m*g*h

v^2 = 2*g*h

v = sqrt(2*g*h)

= sqrt(2*9.8*28)

= 23.42 m/s

D) No. beacsue workdone by gravity does not depend on air resiatnce.

E) Yes. If air resitance does negaitve work.its kinetic energy would be decreased.

F) Yes. when kinetic energy decrased v also decreased.

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