AP Physics System Block Earth

A ball is dropped from rest and falls to the floor. The initial gravitational potential energy of the ball-Earth-floor system is 10 J. The ball then bounces back up to a height where the gravitational potential energy is 7 J. What was the mechanical energy of the ball-Earth-floor system the instant the ball left the floor?

• 0 J

• 3 J

• 7 J

• 10 J

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NGSS.HS-PS3-1

NGSS.HS-PS3-2

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NGSS.HS-PS3-1

NGSS.HS-PS3-2

• infinity

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NGSS.HS-PS2-4

A person holds a book at rest a few feet above a table. The person then lowers the book at a slow constant speed and places it on the table. Which of the following accurately describes the change in the total mechanical energy of the Earth-book system?

• The total mechanical energy is unchanged, because there is no change in the book’s kinetic energy as it is lowered to the table.

• The total mechanical energy is unchanged, because no work is done on the Earth-book system while the book is lowered.

• The total mechanical energy decreases, because the person does positive work on the book by exerting a force that opposes the gravitational force.

• The total mechanical energy decreases, because the person does negative work on the book by exerting a force on the book in the direction opposite to its displacement.

A rubber ball with mass 0.20 kg is dropped vertically from a height of 1.5 m above a floor. The ball bounces off of the floor, and during the bounce 0.60 J of energy is dissipated. What is the maximum height of the ball after the bounce?

• 0.30 m

• 0.90 m

• 1.2 m

• 1.5 m

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NGSS.MS-PS3-1

NGSS.MS-PS3-2

NGSS.MS-PS3-5

A sled slides down a hill with friction between the sled and hill but negligible air resistance. Which of the following must be correct about the resulting change in energy of the sled-Earth system?

• The sum of the kinetic energy and the gravitational potential energy changes by an amount equal to the energy dissipated by friction.

• The gravitational potential energy decreases and the kinetic energy is constant.

• The decrease in the gravitational potential energy is equal to the increase in kinetic energy.

• The gravitational potential energy and the kinetic energy must both decrease.

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NGSS.HS-PS3-1

• The total mechanical energy of the system containing only the block increases from the moment of release to the moment it strikes the ground.

• The total mechanical energy of the block-Earth system remains constant.

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NGSS.HS-PS2-1

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NGSS.HS-PS3-1

A 2 kg object is released from rest near and above Earth’s surface such that the object-Earth system’s gravitational potential energy as a function of time is shown in the graph. Which of the following graphs represents the kinetic energy of the object as a function of time? Assume all frictional forces are considered to be negligible.

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NGSS.HS-PS3-1