A 0.25-kg stone is held 1.5 m above the top edge of a water well and then dropped into it. The well has a depth of 4.5 m. (a) Relative to the configuration with the stone at the top edge of the well, what is the gravitational potential energy of the stone−Earth system before the stone is released? 11.025 Incorrect: Your answer is incorrect. Your response differs from the correct answer by more than 100%. J (b) Relative to the configuration with the stone at the top edge of the well, what is the gravitational potential energy of the stone−Earth system when it reaches the bottom of the well? 0 Incorrect: Your answer is incorrect. The correct answer is not zero. J (c) What is the change in gravitational potential energy of the system from release to reaching the bottom of the well? J

A) 3.579J

B) - 110.36J

C) - 7.38N

Explanation:

A) Gravitational Potential Energy = mgh

Where m is mass, g is acceleration due to gravity and h=height.

Now in this question, height of well is taken to be in area of zero gravitational potential energy, thus

sign is positive.

Gravitational potential energy = mgh = 0.25 x 9.81 x 1.5 = 3.579J

b) In this question, the height is now below the area of zero gravitational potential energy and so h changes to -h.

Thus, sign is negative

Gravitational Potential Energy = mgh = 0.25 x 9.81 x (-4.5) = - 110.36J

c) Again, Gravitational Potential Energy = mgh

But here, since we are looking for change in gravitational potential energy, h = - h1 - h2

Thus,

Gravitational Potential Energy = mg(-h1-h2) = 0.25 x 9.81 x (-1.5-4.5) = - 7.38N

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