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Grades 4-6

This lesson is designed as an innovative learning experience which integrates video-based technology interactively in-corporating student participation. Video and hands-on activities introduce scientific information made real through re-cognition and understanding the phenomena of gravitational force and how it impacts life on our planet. Concepts demonstrating effects of Earth's gravitational force on objects are introduced and explored.
Measuring G's #122
Learning Objectives
Students will be able to:
(per class)

(per student)
Hold a chalkboard eraser in the palm of your hand as you direct students' attention by asking, "How will the eraser react when I invert my hand?" Elicit response, the eraser will fall to the classroom floor. Demonstrate the eraser falling as you invert your hand. Say, "Whenever an object moves, it is propelled by some force. In this demonstration, the force is gravity." Write term on chalkboard, then ask students to define and tell what they know about gravity. (A fundamental physical force manifested by gravitational attraction of the earth's, moon's or other planets' masses for bodies at or near their surface.)

Use a styrofoam cup of water and an empty bucket to demonstrate gravitational pull, free fall and weightlessness. The demonstration shows how a stream of water flowing from a hole in the cup will discontinue its flow during the descent, as you release the cup allowing it to fall into the bucket. Procedure: Punch a small hole in the side of the cup near its bottom; place your thumb over the hole, then fill the cup with water. Ask, "What will happen to the water in the cup if I move my thumb?" Allow time for students to respond, then move your thumb and allow a small amount of water to stream from the cup and fall into the bucket. Quickly, reposition your thumb over the hole. Ask, "If I release the cup allowing it to free fall toward the bucket, will water flow from the hole during its descent?" Allow students to interact as they share their beliefs. Stand on a chair or table, which permits the cup to be dropped from a greater height, hold it directly above the bucket, then release it. Encourage students to explain why no water poured from the hole as the cup fell toward the bucket.

Write free fall, gravitational pull and weightlessness on chalkboard. Encourage students to interact as they discuss their perception of the terms. Lead the discussion to a conclusion that: gravitational force pulls water through the hole if the cup is motionless; and when the cup was released and allowed to free fall toward the bucket, water remained inside because there was an equal amount of force exerted by gravity on the cup and the water.

Say, "Whenever astronauts orbit Earth inside a space craft, they become weightless as they float in space because they and the craft are in a state of free fall. As the cup of water fell toward the bucket, it too was in a state of free fall for the brief period it took to reach the bucket."
Say, "You are going to see a video that explains the relationship of weight and weightlessness to gravity. It also explains why objects have weight." To give students a specific responsibility while viewing say, "Watch and be prepared to tell why you have a specific weight and a classmate has another."

Measuring G's #122
tape immediately following opening credits; audio is, "Measuring G's." PAUSE tape at end of cartoon segment; audio is, "...and you feel weightless." Ask, "What causes you to have weight?" (gravity) Confirm it is the pull of gravity's invisible force that gives weight to objects within its gravitational field. Ask, "G is used to define a unit of force. What is a G equal to?" (the force exerted by gravity on a body at rest; and also used to indicate the force a body is subjected to when accelerated) Write 1 G on chalkboard. Explain: The surface gravity of earth is considered to be 1 G. It is the size, mass and density of a planet that determines its gravitational pull. Write on chalkboard: size, mass, density = gravitational pull. Ask, "Would the surface gravity of a planet smaller in size than earth always have a surface gravity less than 1 G?" Elicit discussion; lead to the conclusion, not necessarily; mass and density may be much greater than earth.

Distribute a copy of Activity Sheet #1, a sheet of notebook paper, a calculator and a pencil to each student. Use a bathroom or other type scale to measure the weight of each student. Record weight in Earth/Actual Weight space on the Activity Sheet chart. Review information and the example to be sure students understand the task. Allow time for completion of the activity; discuss and have students check work for accuracy. Ask, "On which planet did you weigh the least? The most? On which planet was your weight closest to your Earth weight?" Tell students to retain the Activity Sheet. It is needed later in the lesson.

Say, "You now know that all objects are accelerated by gravity at the same rate. At what rate are objects on Earth accelerated by gravity?" (1 G force) Say, "Use this information and explain why in the earlier demonstration, water stopped flowing from the hole in the cup during its free fall (weightless period) as it fell toward the bucket. Allow volunteers to explain the water could not flow from the container because the 1 G force of gravity was pulling on the water and styrofoam cup at the same rate.

Write Galileo on chalkboard. Say, "Galileo was an Italian astronomer and physicist who lived between 1564-1642. It was Galileo who discovered that all objects accelerate at the same rate, in equal increments of time." Allow students to discuss and share their knowledge about Galileo. Ask, "How old was Galileo at the time of his death?" Write 1564-1642 on chalkboard. Affirm Galileo was 78 when he died. Ask, "How many years have passed since his death?" Have students subtract 1996 - 1642 = 354. Say, "No one has disputed Galileo's theory that all objects accelerate at the same rate, in equal increments of time, in all the three hundred fifty four years since his death." Ask, "How might you consider his discovery the beginning of knowledge necessary to develop today's space program?" Allow students to interact; accept all explanations.

Say, "Understanding weightlessness and free fall is key to all travel beyond Earth's atmosphere. In the next video, you are given explanations for both. To give students a specific responsibility while viewing say, "Watch to see an example that proves Galileo's theory true and to find out the boys approximate weight." BEGIN tape as the boy goes through the revolving door leading into the building's lobby. PAUSE tape as adults on the elevator exit on the Observation Deck. Allow time for students to tell the boy's weight is approximately 62 pounds and the Observation Deck is on the 100th floor; record statistics on chalkboard.

Explain the next video segment shows the boy weighing himself on the elevator. Ask, "What do you predict happens to the boy's weight as the elevator descends?" Allow students to make their predictions. To give students a specific responsibility while viewing say, "Watch the video to find out if your prediction is correct." RESUME tape. Allow students to validate their predictions as you PAUSE tape with visual of boy in elevator; audio is, "It works!" Ask, "Was your prediction about the boy's weight change correct?" Allow time for students to share information about their predictions. Instruct students to write a brief explanation stating why the boy's weight decreased during the time the elevator descended.

To give students a specific responsibility while viewing say, "Compare your explanation with the video's explanation as you view the next segment." RESUME tape. PAUSE tape on visual of the boy and adults exiting the elevator. Allow time for students to compare their explanations for the temporarily reduced weight of the boy with the video explanation. Use this activity to evaluate whether the concept of gravity has been mastered by individual students. Make a note to provide individual assistance at a later time for students who evidence the need.

Say, "Exclude outer space and think of situations that would cause you momentary weightlessness." Accept all reasonable responses as: underwater, bungi jumping, falling off a cliff, diving from the high board into a swimming pool, some amusement park rides, etc.; record on chalkboard. Ask students to share any experience they have actually had with momentary weightlessness. Create a grid on the chalkboard; label it Momentary Weightlessness. The grid should include a number of horizontal lines which equals class enrollment plus two or three extras. Begin at bottom and number one through the class enrollment moving up the left margin. Draw (e.g. ten) vertical lines from top to bottom. Move left to right at bottom and label each "grid column" with a student shared weightlessness experience. Poll the class to determine how many students have experienced each example of weight-lessness listed on the grid. Use statistics from each tally to create either a Line or Bar graph. Have students discuss the graph information comparatively.

Say, "At the time you had the weight-lessness experience you contributed toward making the graph, the sensation you felt was a free fall. Had your free fall been scientifically measured, it would have been recorded in terms of G force. In the next video, you are shown how G force is recorded." To give students a specific responsibility while viewing say, "Watch and be prepared to discuss the G force experienced by an object under normal circumstances and G force ex-perienced during other various activities." RESUME tape. STOP tape on visual of boy again on elevator looking at the scale. Elicit discussion among students. Include: "What pulls a roller coaster downhill?" (gravity) "How would you define free fall and where did the term originate?" (a feeling or sensation of lightness; space program/astronaut) "Under normal cir-cumstances, how many G's do you feel?" (1 G) Encourage students to internalize the familiar sensation of 1 G force of gravity (normal activity) as you have them compare it to the sensation they might experience if riding in a convertible traveling 75 MPH, skiing down a mountain or roller blading on a sidewalk.

Students should be able to explain the weight of a person (object) depends on the G force they are subjected to. Record on chalkboard, then have students discuss: 1 G = force of gravity at sea level; 0 G = no force of gravity due to a state of weightlessness; and 2 G's = twice the force of gravity, etc.

Explain the effects of weightlessness on the human body is a great concern to scientists and astronauts. Ask students to share effects they felt on an occasion when they rode in a roller coaster. Ask students to respond and qualify their answer to the question, "Do you believe an astronaut's height changes when in space?" Explain: "Some of us are slightly taller immediately after we get out of bed in the morning." Have two volunteers stand and demonstrate location of one another's vertebrae. Write vertebrae on chalkboard. Say, "Separating and cushioning the vertebrae is a substance called cartilage. During periods of activity the cartilage becomes more tightly compressed between the vertebrae. When a person is at rest, weight is shifted allowing the cartilage to expand, thus causing the individual to appear slightly taller." Suggest students have someone measure their height before going to bed and immediately upon arising the next morning. On the appropriate day(s), provide time for students who engaged in the experiment to share results.

Write on chalkboard: Which mineral does the human body lose during space travel? What happens to muscle tone while traveling in space? To give students a specific responsibility while viewing call attention to the questions, then say, "Watch the next video and be prepared to answer the questions." BEGIN tape with visual of a male astronaut in a space craft standing as he types. STOP tape after female narrator says, "...but they don't stop it completely." Video is an astronaut lifting weights for body tone. Engage students in interaction as they discuss calcium is the mineral lost by the human body in space; and an individual's muscle tone is reduced during space travel.

Pre-prepare the following one week prior to presenting the lesson (for immediate observation of result) or prepare in view of students at this point in lesson and encourage observation throughout the week. DEMONSTRATION: Place three small chicken bones in a transparent container, cover bones with vinegar and replace the container's lid. One week is necessary for the vinegar to extract calcium rendering the chicken bones rubbery and easily bent. Remove bones; allow students to experience the characteristics of a bone that has had its calcium extracted. Use this opportunity to emphasize need for maintaining a well balanced diet which includes all nutrients, vitamins and minerals necessary to promote growth and maintain health.

Ask, "What will happen to an astronaut's bones if a significant amount of calcium is lost?" Elicit discussion drawing conclusion that loss of calcium will cause the bones to bend and break easily. Relate discussion to the condition (or anticipated condition) of the chicken bones demonstration. Emphasize that great care is taken in the development of a routine exercise program to be followed and special diet to be consumed whenever humans travel in space.

Plan a field trip to an amusement park. Construct a G Meter as shown on the video, then use it to measure the G force on selected rides.

There are twenty-eight Challenger Space Centers throughout the United States. If one is located reasonably convenient to your community, plan a field trip. Students will have an opportunity to participate in a simulated space mission and learn the jobs of astronauts and mission control personnel.

Invite a professional scuba diver to visit your classroom if you live in a community where individuals in this profession are located. Ask them to discuss how G force affects their work, how it can impose limitations on their jobs and why knowledge of G force is critical to safety on the job. If professional scuba divers are not an option, Police Departments in most large cities have a Tactical Force which includes officers with scuba diving skills.
Distribute a copy of Activity Sheet #2 to each student. Instruct them to use their "actual weight" figure from Activity Sheet #1 and create a Bar or Line Graph. The graph will show the individual's weight on each planet in the Solar System. Display the graphs in your classroom.

Have students select various objects and drop them from a height. Prior to the drop, have students predict which object(s) will reach the ground first.

The center of gravity is the point where an object can be balanced. Use a coat hanger, place a fork on a potato at different locations, etc., and have students experiment with the concept.

If you have an ice skater in your class or school, ask them to discuss the importance of being knowledgeable about center of gravity and how G force can impact per-formance in this sport.

Study muscle tone and the effects of exercise on the body. Have students design a program of exercise that could be beneficial to astronauts.

Language Arts
Read: The Day We Walked on the Moon and Apollo 13 Have students use imaginations and compose newspaper headlines they believe could be applicable to space exploration in the year 2005.

Master Teachers: Jaci Stewart and Anna Sedoris

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