Conservation of Mechanical Energy

A child plays on a swing and reaches the highest point on one side before swinging back down. What happens to the total mechanical energy of the child-swing system as the child swings?

• It increases as potential energy is converted to kinetic energy.

• It remains constant, though energy changes between potential and kinetic.

• It decreases because kinetic energy is converted to potential energy.

• It remains constant, though energy changes from kinetic to potential.

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NGSS.MS-PS3-2

NGSS.MS-PS3-5

A skier is at the top of a slope and skis down to the bottom. Which of the following best describes the transformation of energy?

• Kinetic energy is transformed into potential energy as the skier descends, keeping total mechanical energy constant.

• Kinetic energy and potential energy both decrease, keeping total mechanical energy constant.

• Potential energy is transformed into kinetic energy as the skier descends, keeping total mechanical energy constant.

• Potential energy increases and kinetic energy decreases, reducing the total mechanical energy.

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NGSS.MS-PS3-2

NGSS.MS-PS3-5

A 2 kg ball is dropped from a height of 10 meters, assuming no air resistance. Which of the following statements is true just before it hits the ground?

• Its kinetic energy and potential energy are equal.

• Its kinetic energy is at a maximum and its potential energy is at a minimum.

• Its kinetic energy is at a minimum and its potential energy is at a maximum.

• Its kinetic energy is at a minimum and its potential energy is at a minimum.

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If mechanical energy is conserved in a system, the energy at any point in time can be in the form of...

•  kinetic energy.

   

• gravitational potential energy

   

• elastic potential energy

   

• all of the above

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NGSS.MS-PS3-4

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Which of the following is true of the conservation of energy in a closed system?

 

• A. Kinetic energy is always conserved.

   

• B. Potential energy is always conserved.

   

• C. Mechanical energy is always conserved.

   

• D. Total energy is always not conserved.

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The mechanical energy of a system of objects is...

• the sum of kinetic energy and gravitational potential energy.

• the sum of kinetic energy and elastic potential energy.

• the sum of kinetic energy and all relevant forms of potential energy.

• the sum of all forms of energy.

3. Mechanical energy is NOT conserved when...

•  A. gravitational potential energy is converted to kinetic energy.

   

• B. kinetic energy is converted ONLY to gravitational potential energy.

   

• C. kinetic energy is converted to JUST elastic potential energy.

   

• D. friction is not negligible.

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NGSS.MS-PS3-5

The rock rolls down a hill. The potential energy of the rock when it was on top of the hill compared to its kinetic energy at the lowest point is _____.

• equal

• lower

• higher

• not related

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NGSS.MS-PS3-4

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The magnitude of the kinetic and potential energy of a free fall for the first 2 seconds of its fall was given. What is the potential and kinetic energy of the apple before hitting the floor

• PE= 8J; KE = 0

• PE= 8J; KE = 8J

• PE= 0; KE = 8J

• PE= 0; KE = 4J

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NGSS.MS-PS3-2

NGSS.MS-PS3-4

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At which point will the pendulum have the greatest potential energy?

• A

• B

• C