Conservation of Energy

In physics, a _____ is a group of related objects that interact with each other and form a complex whole.

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NGSS.HS-PS3-2

What term is used to describe a system that loses energy to objects that are not part of the system?

• open

• closed

• raised

• low

A box is released from rest and slides down a ramp in a closed system. Even though the box speeds up, its kinetic energy at the bottom of the ramp is less than the potential energy that it had at the top of the ramp.

What best explains why the box’s final kinetic energy is less than its initial potential energy?

• In a closed system, kinetic energy is always less than potential energy.

• Some potential energy was converted into thermal energy due to friction.

• The acceleration due to gravity became smaller as the box slid down the ramp.

• In a closed system, total energy is constantly being lost to outside objects.

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NGSS.HS-PS3-1

NGSS.HS-PS3-4

What does the law of conservation of energy state about energy in a closed system?

• Energy cannot be created or destroyed.

• Energy can be created but not destroyed.

• Energy can be destroyed but not created.

• Energy can be either destroyed or created.

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NGSS.HS-PS3-2

Jonesy, a cat, has a favorite toy that is made up of a squeaky ball at the end of a string. The toy makes up a closed system. Ellen dangles the toy so that the ball swings down and then swings back up again.

Ignoring any friction, how are kinetic and potential energy related to each other as the ball swings back and forth?

• As the ball moves upward, both kinetic and potential energy decrease.

• As the ball moves downward, both kinetic and potential energy increase.

• As the ball moves upward, kinetic energy decreases and potential energy increases.

• As the ball moves downward, kinetic energy decreases and potential energy increases.

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NGSS.MS-PS3-4

NGSS.MS-PS3-5

What best describes the energy in a closed system at the beginning of a day and the energy at the end of the same day? Check all that apply.

• Some energy can disappear after it has caused motion.

• Some energy can be changed from one form to another.

• Some energy can be lost to the environment around the system.

• The total initial energy will be equal to the total final energy.

• Friction can cause the amount of thermal energy to increase.

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NGSS.MS-PS3-4

NGSS.MS-PS3-5

Which equation represents the law of conservation of energy in a closed system?

• KE_i + PE_i = KE_f + PE_f

• PE_i + PE_f = KE_i + KE_f

• KE_i – KE_f = PE_i – PE_f

• KE_i – PE_f = PE_i – KE_f

When an object is not in motion, it can still have a form of energy. What form of energy does an object have due to its distance from Earth?

• kinetic energy

• thermal energy

• gravitational potential energy

• electrical potential energy

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NGSS.MS-PS3-2

A 7.00 kg bowling ball is held 2.00 m above the ground. How many Joules does the bowling ball have due to its position? Round to the nearest whole number.

A 440 kg roller coaster car is going 26 m/s when it reaches the lowest point on the track. If the car started from rest at the top of a hill, how much higher was that point (in meters) on the frictionless track than the lowest point? Round to the nearest whole number.

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NGSS.HS-PS3-1