80 Newton’s Laws of Motion

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80 Newton’s Laws of Motion

Key Vocabulary

• acceleration• balanced forces• inertia• force• friction• net force• unbalanced forces

80 Newton’s Laws of Motion

Read the introduction and look for key ideas

This image of Isaac Newton appears in one of his books,

published in the 1600s.Newton wrote Laws of

Motion in Latin.

80 Newton’s Laws of Motion

What relationships between force and motion did Newton discover?

Isaac Newton

80 Newton’s Laws of Motion

Complete the “Before” column of student sheet 80.1, “Anticipation Guide: Laws of Motion”

80 Newton’s Laws of Motion

Complete the reading

Be sure to complete the Stopping to Think questions.

80 Newton’s Laws of Motion

Stopping to think 1

Which has more inertia: a heavy ball or a light ball rolling at the same speed in the same direction? Think about which one is more resistant to a change in motion.

80 Newton’s Laws of Motion

Stopping to think 2

What would happen to a baseball if you could throw it in outer space? Explain in terms of inertia and friction.

80 Newton’s Laws of Motion

Stopping to think 3

A car travels along a straight road at a steady 40 mph. Are the forces on the car balanced or unbalanced? Explain.

80 Newton’s Laws of Motion

Stopping to think 4

Can a light object that was hit with a small force accelerate as rapidly as a heavier object hit with a big force? Why or why not?

80 Newton’s Laws of Motion

Stopping to think 5

If you hold a backpack in your hand, the force of gravity pulls it downward. What force keeps it from falling to the ground?

80 Newton’s Laws of Motion

Friction and force

Friction – the force that exists at the boundary between any two pieces of matter that are in contact with each other.

Net Force – the combined force (magnitude and direction) acting on an object or system.

What is the relationship between net force, balanced forces, and unbalanced forces?

Share your answer with the class.

80 Newton’s Laws of Motion

Complete the “After” column of student sheet 80.1, “Anticipation Guide: Laws of Motion”

80 Newton’s Laws of Motion

Analysis question 1

Spaceships that travel millions of miles into outer space use very little fuel. How can they go so far on so little fuel?

80 Newton’s Laws of Motion

Analysis question 2

Use Newton’s laws to explain why it is easier to turn a truck when it is empty than when it is carrying a heavy load.

80 Newton’s Laws of Motion

Analysis question 3

An engine can exert a force of 1,000 newtons. How fast can this engine accelerate:

a. a 1,000-kg car?

b. a 2,000-kg car?

80 Newton’s Laws of Motion

Analysis question 4

Use Newton’s third law to explain why a blown up but untied balloon will fly around the room when you let it go?

80 Newton’s Laws of Motion

Analysis question 5

Motor oil, axle grease, and other lubricants are slippery. Why do you think people spend the money to put these lubricants in their cars?

80 Newton’s Laws of Motion

What relationship between force and motion did Newton discover?

As the train travels at constant speed, the engine must produce enough force to equal the friction caused by the air and the wheels on the track.

80 Newton’s Laws of Motion

Key vocabulary definitions

Acceleration - The rate at which an object changes speed and/or direction.

Balanced forces - When the magnitude and direction of more then one force acting on an object results in zero net force.

80 Newton’s Laws of Motion

Key vocabulary definitions

Force - A push or pull.

Inertia - The resistance of an object to changes in its motion.

80 Newton’s Laws of Motion

Key vocabulary definitions

Friction - A force that exists at the boundary between any two objects that are in contact with each other.

Net force - The combined force (magnitude and direction) acting on an object.

80 Newton’s Laws of Motion

Key vocabulary definitions

Unbalanced forces - When the magnitude and direction of more than one force acting on an object give a net force unequal to zero.