You drop a 2.50 kg textbook to a friend who stands on the ground at distance D =

Question

You drop a 2.50 kg textbook to a friend who stands on the ground at distance D = 10.0 m below. Your friend's outstretched hands are at distance d = 1.50 m above the ground.

(a) How much work Wg does the gravitational force do on the book as it drops to her hands?

(b) What is the change U in the gravitational potential energy of the textbook-Earth system during the drop?

(c) If the gravitational potential energy of that system is zero at ground level, what is its potential energy U when the textbook is released?

(d) If the gravitational potential energy of that system is zero at ground level, what is its potential energy U when the textbook reaches the hands?

(e) How much work Wg is done on the textbook by its weight as it drops to your friend's hands if U is 100 J at the ground level.

(f) What is the change U in the gravitational potential energy of the textbook-Earth system during the drop if U is 100 J at the ground level.

(g) Find U at the release point when U is 100 J at the ground level. Incorrect: Your answer is incorrect. J (h) Find U at the hands when U is 100 J at the ground level.

Explanation / Answer

W= F.s = 2.5X 9.8 X (10-1.5) = 208.25 J

change in P.E= 2.5 x 9.8 x (1.5- 10) = -208.25 J

U when book is released = 245 J

U when book is reached = 36.75 J

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