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A 0.19-kg stone is held 1.2 m above the top edge of a water well and then droppe

ID: 1356722 • Letter: A

Question

A 0.19-kg stone is held 1.2 m above the top edge of a water well and then dropped into it. The well has a depth of 5.4 m.

(a) Taking

y = 0

at the top edge of the well, what is the gravitational potential energy of the stone–Earth system before the stone is released?
J

(b) Taking

y = 0

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?
J

(c) What is the change in gravitational potential energy of the system from release to reaching the bottom of the well?
J

Explanation / Answer

The gravitational potential energy is the energy change that would occur between two points due to gravity and can be written as follows:

PE = m * g * h

a) E1 = 0.19*9.81*1.2 = 2.236 J

b) E2 = 0.19*9.81*(-5.4) = -10.06 J

c) Change = E2 - E1 = -10.06 - 2.236 = -12.296 J