Kinetic Energy

Kinetic Energy

Middle School

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Learning Objectives

• Define kinetic energy and its relationship with an object's mass and speed.

• Describe the relationship between an object's speed and its kinetic energy.

• Explain the relationship between an object's mass and its kinetic energy.

• Compare the kinetic energy of different objects in real-world examples.

Key Vocabulary

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Kinetic Energy

The energy an object has because of its motion, which depends on its mass and speed.

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Mass

The measure of how much matter is in an object, a key factor in its kinetic energy.

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Speed

The rate at which an object covers distance and a major factor in its kinetic energy.

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Directly Proportional

A relationship in which two variables increase or decrease together, such as distance and time at constant speed.

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Linear Relationship

A relationship where an increase in one variable results in a steady, proportional increase in another.

The Role of Speed in Kinetic Energy

• When an object's speed increases, its kinetic energy increases.

• When an object's speed decreases, its kinetic energy also decreases.

• A faster car has much more kinetic energy than a slower one.

Multiple Choice

What happens to an object's kinetic energy when its speed increases?

• Its kinetic energy increases.

• Its kinetic energy decreases.

• Its kinetic energy stays the same.

• Its kinetic energy becomes zero.

Multiple Choice

Which statement correctly describes what happens to a car's kinetic energy?

• As the car's speed decreases, its kinetic energy decreases.

• As the car's speed decreases, its kinetic energy increases.

• The car's kinetic energy is not related to its speed.

• Only a car that is speeding up has kinetic energy.

Multiple Choice

A driver presses the brakes to slow down a car. Which statement provides the best explanation for what happens to the car's kinetic energy?

• The kinetic energy decreases because the car's speed is decreasing.

• The kinetic energy increases because the brakes are creating friction.

• The kinetic energy stays the same because the car is still moving.

• The kinetic energy is converted into potential energy.

The Role of Mass in Kinetic Energy

• An object's kinetic energy increases as its mass increases.

• The change from mass is less dramatic than the change from speed.

• A heavier tennis ball has more kinetic energy than a lighter wiffle ball.

Multiple Choice

What happens to an object's kinetic energy as its mass increases?

• Kinetic energy increases

• Kinetic energy decreases

• Kinetic energy stays the same

• Kinetic energy becomes zero

Multiple Choice

Why does a heavier tennis ball have more kinetic energy than a lighter wiffle ball when traveling at the same speed?

• The tennis ball is moving faster

• The wiffle ball has more air inside

• The tennis ball has more mass

• The wiffle ball is easier to throw

Multiple Choice

If you want to make the least dramatic change to an object's kinetic energy, which property would you alter?

• Changing the object's speed

• Changing the object's mass

• Changing the object's color

• Changing the object's direction

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Common Misconceptions

Misconception	Correction
Mass and speed have an equal effect on kinetic energy.	A change in speed has a much greater impact on kinetic energy.
An object has kinetic energy when it is stationary.	Kinetic energy is the energy of motion. An object at rest has none.
If two objects have the same speed, they have the same kinetic energy.	Kinetic energy also depends on mass. The object with greater mass has more.

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Summary

• An object's kinetic energy depends on its mass and speed.

• An object's speed has a major effect on its kinetic energy.

• More mass means an object has more kinetic energy.

• To compare kinetic energy, look at both mass and speed.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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• 4