5-5 Conservation of Energy

5-5 Explain: Conservation of Energy

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Mr. Custer

Pre Assessment

Show me what you know!

Poll

I can create energy.

• yes

• no

Multiple Choice

A ball is projected into the air. Where is potential energy the greatest?

Multiple Choice

Which point on the roller coaster's path represents the maximum potential energy?

Three Types of Systems

Exchange both energy and matter with their surroundings.

Open Systems

Exchange only energy with their surroundings.

Closed Systems

Do not exchange anything with their surroundings.

Isolated Systems

Multiple Choice

What type of system is shown in the picture?

• Open

• Closed

• Isolated

Multiple Choice

What type of system is shown in the picture?

• Open

• Closed

• Isolated

Multiple Choice

This soup cooking in the open pot is an example of which type of system?

• Open

• Closed

• Isolated

Multiple Choice

Putting a lid on the cooking soup pot is an example of what type of system?

• Closed

• Open

• Isolated

Multiple Select

Choose all of the examples of Open Systems.

• A sealed bottle of water with the cap on

• An opened full bottle of water with no cap

• An opened empty water bottle with no cap

• An empty bottle of water with the cap on

The Law of Conservation of Energy

Energy is not created nor destroyed. Just transferred.

​Here's an example:

​Atoms in the Sun's core fuse together and release light energy.

The light hits plants. Plants turn that into chemical energy.​

​Humans can eat those plants for energy, which is the chemical energy being converted to thermal energy.

However much energy there was since the Big Bang, is exactly how much energy there is today.

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Energy doesn't randomly appear or disappear - it changes forms!

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The Total Amount of Energy is Constant!

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Multiple Choice

In July 1971, Apollo 15 astronaut Dave Scott performed an experiment on the Moon. Scott held a feather and a hammer at the same height, and let them drop at exactly the same time. Both fell at the same rate and hit the ground at the same time.

At which time did the hammer have the greatest gravitational potential energy?

• time 1

• time 3

• times 1 and 3

• time 2

Multiple Choice

In July 1971, Apollo 15 astronaut Dave Scott performed an experiment on the Moon. Scott held a feather and a hammer at the same height, and let them drop at exactly the same time. Both fell at the same rate and hit the ground at the same time.

At which time did the feather have the greatest kinetic energy?

• time 1

• time 2

• time 3

• both times 1 and 3

Multiple Choice

In July 1971, Apollo 15 astronaut Dave Scott performed an experiment on the Moon. Scott held a feather and a hammer at the same height, and let them drop at exactly the same time. Both fell at the same rate and hit the ground at the same time.

Which of the following is true about the relationship between the gravitational potential energy and the kinetic energy of the hammer?

• The kinetic energy + gravitational potential energy stays the same at all times.

• The kinetic energy and potential energy are the same as each other at all times.

• The kinetic energy at time 1 is equal to the gravitational potential energy at time 1.

• The kinetic energy at time 3 is equal to the gravitational potential energy at time 3.

Kinetic Energy is directly related to mass and velocity.

Calculating Kinetic Energy

Multiple Choice

Calculate the kinetic energy of a running back that has a mass of 80 kg and is running as a velocity of 8 m/s.

• 320 J

• 640 J

• 2560 J

• 5120 J

Multiple Choice

What is the kinetic energy of a soccer ball which has a mass of 0.8 kg and is kicked with a velocity of 10 m/s?

• 40 J

• 8 J

• 4 J

• 80 J

E_G is directly proportional to both mass and height.​

Calculating Gravitational P.E.

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Multiple Choice

There is a clock at the top of a tower that is 45m high. The clock has a mass of 20 kg. Calculate its gravitational potential energy.

• 20,250 J

• 9.8 J

• 900 J

• 9,000 J

Multiple Choice

What is the GPE of a 0.3 kg apple on top of a 1 m tree?

• 0 J

• 3 J

• 0.3 J

• 30 J