6-8 > Physical Science
 Grade level: 6-8 Subject: Physical Science Duration: 3 class periods
 Student Objectives | Materials | Procedures | Assessment | Vocabulary | Academic Standards

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Student Objectives
• Watch the segments "Friction" and "Constant Speed" inDiscovery Science Library: The Basics: Physical Science
• Write a paragraph explaining how friction and gravity affect four sports.
• Draw a picture illustrating the effect of friction and gravity on these sports.
Materials
• Discovery Science Library: The Basics: Physical Sciencevideo
• Newsprint and markers
• Computer with Internet access
• Paper and pencils
• Markers and colored pencils
Procedures
1. Begin the lesson by asking students if they are familiar with the terms "friction”"and "gravity." Write their ideas on a sheet of newsprint. Then explain to students that gravity is a force that keeps objects in motion, and friction works in opposition to gravity to help objects stop. Together these forces affect the way almost everything moves on Earth.
2. Tell students that they will explore how friction and gravity affect the way sports are played. Working with a partner, have students focus on the following sports:
• auto racing
• skiing
• skating
• bicycling
3. To begin their research, have students watch the segments "Friction" and "Constant Speed." In addition, the following Web sites have information on this topic:
4. After students have finished watching the program and completed their research, ask them to write a paragraph describing how friction and gravity affect the way these sports are played. Make sure students include an illustration showing the effect of the forces on each sport.
5. To help students organize their paragraphs, have them use the following points as a guide:
• Name of the sport
• Factors in the sport: For example, to go fast, to stop quickly, to travel consistently for a long period of time, or a combination
• How friction and gravity affect the sport
• How people control the forces
6. During the next class period, ask students to share their ideas. Make sure they understand that in a sport such as skating, athletes want to decrease friction so that they will go faster. In biking, however, athletes control how fast they go by pedaling faster or pedaling slower. Reiterate that the forces of friction and gravity affect all sports.
7. Conclude the lesson by asking students what they learned about forces and sports. How will this knowledge affect they way they participate in sports? Can it help them become better athletes?
Assessment
Use the following three-point rubric to evaluate students' work during this lesson.
• 3 points: Students were highly engaged in class and small-group discussions and produced clear and accurate paragraphs and illustrations, with all the requested components.
• 2 points: Students participated in class and small-group discussions and produced adequate paragraphs and illustrations, with most of the requested components.
• 1 point: Students participated minimally in class and small-group discussions and produced incomplete paragraphs and illustrations, with little or none of the requested components.
Vocabulary
acceleration
Definition:The rate at which an object increases speed
Context:In a bicycle race, riders pedal faster for greater acceleration.

air resistance
Definition:The force on an object pulling it upward; the greater the surface area of an object, the greater the air resistance
Context:The surface area of a leaf is greater than that of an acorn, so air resistance is greater, and the leaf falls more slowly than the acorn.

force
Definition:A push or pull working on an object
Context:Kicking a soccer ball is an example of a force.

friction
Definition:The force between two substances rubbing against each other
Context:Ice skaters add a thin layer of water to the ice to decrease friction and move faster.

gravity
Definition:The force working on objects that pulls them toward each other
Context:The force of gravity keeps roller coasters moving down a steep hill.