Day 4 - Friction and Inertia

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Toy Cars

Note: This lesson is best taught after the Day 3 lesson, "Friction." If students have not participated in that lesson, make sure that you define the word "friction" and give a short explanation.

Objectives:

1. Students will observe that different surfaces produce different amounts of friction.
2. Students will understand the concept of inertia and learn the importance of seat belts in cars.

Vocabulary:

Friction: The resistance that results when two surfaces rub against each other.

Inertia: A resistance to a change in motion

Newton's First Law of Motion: An object at rest or in motion will remain that way unless acted on by an external force.

Materials needed:

• a car, ball, or top for each group
• 5 ramps
• 5 smooth surfaces
• 5 carpet strips
• 5 felt strips
• 5 sandpaper strips
• 5 Matchbox cars
• 5 yardsticks
• books or other objects to use to prop up the ramps and to crash cars into "Car Race" observation sheet for each group or student (25)
• 5 protractors
• clay

Introduction:

Begin by asking students to define the word "friction" (the resistance that results when two surfaces rub against each other). Ask them for some examples of things that show a lot of or very little friction. (Ice skating has very little friction, pulling something heavy without wheels may have a lot of friction).

Ask, "If you push a ball on a wood floor what will happen?" (It rolls away) "Does a wood floor produce a lot of friction?" (No. There is little friction between the ball and the floor.) "What if you don't touch the ball? What will happen to it?" (It will just sit there.) Explain that this is what we call "inertia" -- a resistance to change in motion.

Tell students that in this lesson they will learn some more about friction and they will learn about Newton's First Law of Motion. Explain that Isaac Newton was a physicist in the seventeenth century. One of the important things he did was formulate three laws of motion. The first law states that an object at rest will stay at rest or an object in motion will stay in motion unless acted upon by an external force.