The $20.00 Challenge
Ask your students if they think they could catch a $20.00 bill before it hits the floor using only their thumb, index finger, and middle finger.
Select one of your students to come up and try your challenge.
Instruct your student to extend an arm out perpendicular from the body and extend the hand straight out in front of them.
Next, instruct your student to put his/her thumb, index finger, and middle finger together in a pinching action.
Have the student open the closed fingers about an inch apart.
Place a new $20.00 bill in between the student's open fingers, holding it lengthwise with your thumb and index finger.
Instruct your student that you are going to let go of the $20.00 bill and when you do, he/she may only use the thumb, index finger, and middle finger of the extended arm to catch the currency. The student cannot move the arm from the extended position. If the student can catch it, he/she gets to keep the money.
Discuss with your students why they think it was impossible for the student to catch the $20.00 bill. Bring up a few more students to prove your point that no one in the class can catch the currency before it hits the ground. (The Earth's gravitational pull makes this challenge impossible to win. As you release the currency and your student closes his/her fingers, the currency has already passed through the fingers. Try it several times on yourself before you attempt it in the classroom to ensure that you have the whole technique worked out.)
Learning Activity: I'm Free Falling
Ask students to break down into their study groups.
Have students punch a small hole through the side of the styrofoam/plastic cup on its side near the bottom.
Have students place their thumb over the hole, then fill the cup with water up to the line just before the top rim of the cup.
Ask the students what will happen to the water inside the cup if they remove their thumb from over the hole.
Have them write down their predictions. Allow ample time for the students to respond to the question.
Have them remove their thumbs from the hole and allow a small amount of water to stream from the hole and fall into the empty Tupperware tray they have placed directly under the cup on top of the drop cloth.
Quickly have them place their thumb over the hole.
Refill the cup up to the line just below the top rim of the cup.
Ask the students, "If you were to release the cup, allowing it to fall toward the tray, will water flow from the hole during its fall?" Again, allow students ample time to respond to your question and to interact as they share their thoughts and ideas.
Have a student in each study group stand on top of a chair. This allows the cup to be released from a greater height.
Hold the cup over the Tupperware tray and let it go.
Elicit student explanations as to why none of the water poured from the hole as the container fell toward the tray.
Write the terms "Free Fall," "Gravitational Pull," and "Weightlessness" on the overhead.
Ask students to sit down in their study groups and discuss their understandings of the terms on the overhead as they apply to the styrofoam cup. (The gravitational force pulls the water through the hole in the container as long as the container remains motionless. But when the container is set in motion (dropped) and allowed to free fall toward the empty tray, the water remains inside the container because there is an equal amount of gravity being exerted on the container and the water inside the container.)
Insert 3-2-1 Classroom Contact, Episode #22: "Gravity" into your VCR.
Provide your students with a FOCUS FOR MEDIA INTERACTION, asking your students to listen for and record the definitions or explanations of what is gravity, what is weightlessness, and what is free fall. PLAY the videotape from the visual cue of the cartoon boy sitting on the chair. This segment is found right after the opening title of the series and segment. PAUSE the videotape to record information at the end of the cartoon segment; the audio cue here is "...and you feel weightless." (Gravity is the force that pulls on you. It is what keeps chairs on the ground and you in them. If there were no gravity pulling on you, you would be weightless. If you were in space orbiting the Earth, you and everything in the spaceship are falling at the same rate. Since nothing is pulling on anything else, you are in a state of free fall.)
Allow ample time for your students to record their answers on the Focus for Media Interaction Sheet. As your students are recording their information, write on the overhead the words, "Gravity," "G," "Free Fall," and "Weightlessness." As a class, have your students discuss their findings and record the class consensus for each term on the overhead.
On a new transparency, write the name, "Galileo." Explain to your students that Galileo was a scientist whose forte was in the fields of astronomy and physics and that he lived between the years 1564-1642. Explain to your students or elicit from them the fact that Galileo was the person who discovered that all objects fall at a constant rate of speed no matter what their size or weight is over equal periods of time. Ask your students to figure out how old Galileo was at the time of his death (1642 - 1564 = 78 years old). Ask them how many years has it been since his death to present day (2001 - 1642 = 359 years).
Say to your students, "You mean to tell me that in 359 years nobody has been able to prove Galileo wrong?! That no one has tried to dispute his theory that all objects accelerate at a constant rate over equal periods of time?! Do you think his discovery more than 359 years ago helped people develop space travel?" Allow your students ample time to discuss their points of view. Try to bring this discussion to an amicable conclusion -- you can always allow your students the opportunity to go back later.
Provide your students with a FOCUS FOR MEDIA INTERACTION, asking your students to record Paco's weight when they see it, and then stand up. RESUME the videotape at the visual cue of Paco going through the revolving doors. PAUSE the videotape to discuss student findings as all of the passengers exit the elevator at the observation deck. The audio cue here is "...I know." Your students should be standing up (Paco's weight is approximately 60 pounds). Again, allow time for your students to record their findings on the Focus for Media Interaction Sheet.
Provide your students with a FOCUS FOR MEDIA INTERACTION, asking your students to look for and record Paco's average weight, and the floor the observation deck was on. When they have recorded this information, ask them to clap their hands. RESUME the videotape. PAUSE the videotape when a student claps his or her hands. (The observation deck is on the 107th Floor. Paco's average weight is approximately 45 pounds.) Again, allow your students ample time to record their answers. Discuss with your students why they think Paco's weight decreases on the way down in the elevator.
What would allow that to happen? Ask your students to figure out the number of pounds Paco lost going down in the elevator (60 - 40 = 20). Ask your students to take a few moments and briefly write down on the Focus for Viewing Sheet their reasoning behind the decrease in the scale reading.
Explain to your students that in the next section we are going to compare our explanations with that of the video. FAST FORWARD the videotape to the visual cue of Paco standing in the elevator with a crowd of people looking at him squatting on the scale. Provide a FOCUS FOR MEDIA INTERACTION, asking your students to view the next segment and record why Paco's weight decreases on the way down in the elevator. RESUME the videotape. PAUSE the videotape to discuss student findings at the visual cue of the passengers exiting the elevator. (As gravity is pulling Paco down and the elevator is moving away from him, Paco is not pushing down on the elevator floor as much as he was before the elevator began to move down.)
Allow students time to compare their explanations with that of the videotape. Lead this discussion to the conclusion that the motion/downward movement of the elevator temporarily reduced Paco's weight because he was exerting less pressure on the scale.
Ask your students, "Have you ever experienced the feeling of being weightless?" Have them cite specific examples of everyday activities or events where this has happened to them. Record their responses on a new overhead transparency. Explain to your students that at the time of their so-called weightless experience, they actually encountered a phenomenon called "free fall." Ask your students, "Does anyone know how scientists measure free fall?" (G force.) If you receive no correct responses from your students, tell them that as a group you are going to discover just what that measurement is.
REWIND the videotape to the visual cue of Paco standing on the scale; the audio cue here is, "...it works!" Provide your students with a FOCUS FOR MEDIA INTERACTION, asking your students to record what G force is, the normal Gs we feel on a daily basis, and what makes roller coasters work the way they do. PLAY the videotape. PAUSE the videotape to record information at the visual of Paco standing on the scale in the elevator. (G force is the measurement of how much gravitational force is being applied to a body of mass. On a daily basis, we feel 1G of force being applied to our bodies. Once the cars are pulled up the first hill by the chain mechanism, gravity takes over and makes the cars travel the rest of the track.) Allow ample time for your students to record their answers on their worksheet.
Ask your students, "If my weight right now as I stand here in front of you is equal to 1G, how many Gs would it take to double my weight?" (2) "How many Gs would it take to make me weigh nothing?" (0) Say to your students, "So far we have talked about gravity, weightlessness, free fall, and G force or gravitational pull as they all relate to us here on earth. What do you think happens to astronauts in orbit in outer space?" Have students discuss and recall scenes and events they have seen in movies, the news, or on television in general.
EJECT 3-2-1 Classroom Contact, Episode #22: "Gravity."
Lab Experiment 1: It's A Matter of Weight
Have students break down into their study groups.
Have students attach the weight or bag of pennies to the scale.
Have them record the weight from a standing/hanging position.
Have each member in the group take turns going through the following sequence:
Repeat Step 4 three more times.
- Lay the scale flat on the table with the weight attached on the lab top or desktop.
- Lift the scale so that the weight is resting on the desktop. (The scale should read "O.")
- Rapidly lift the scale in an upward direction.
- Have study partners watch the scale and record the highest reading they see on their lab sheet.
Have each member in the group take turns going through the following sequence:
Repeat Step 5 three more times.
- Have each group member hold the scale with the weight hanging.
- Have students quickly lower their hand in a downward motion.
- Have study partners watch the scale and record the lowest reading they see on their lab sheet.
Repeat Step 6 three more times.
- Ask the study group members to again hold the scale with the weight hanging in midair.
- Instruct each member of the study group to watch the scale as their study partners let the scale and the weight go and it falls on the padding.
- Have students record the approximate weight they saw on the lab sheet.
Have students answer the remaining questions on the lab sheet.
Lab Activity 2: Space Weight
Ask your students to log on to the Your Weight on Other Worlds site at www.exploratorium.edu/ronh/weight/index.html. Provide students with a FOCUS FOR MEDIA INTERACTION, asking them to enter their personal weight on the site, and to record their weight conversions on the various planets, moons, and systems on the lab activity site.
Have your students calculate the number of Gs each planet, moon, or star would exert on their bodies if they actually lived on them. (Converted Weight / Actual Weight = # of G's)
As a group, the students are to create a bar graph for each planet using their personal weight data for comparison against those from the other study groups.
As a group the students are to create a line graph showing the number of Gs each planet, moon, or star would exert on their bodies.
Students can read Apollo 13 and other space-related books. Have them use their imaginations to create a front page of a newspaper for the year 2048 with stories and headlines they believe could be happening that relate to space exploration.
Using acquired knowledge of gravity, gravitational pull, and free fall, students can design their own parachutes to safely carry precious cargo, such as an egg, from the top of the school building to the ground below without damaging it.
Students can be encouraged to investigate various shapes and their aerodynamic qualities using free fall. They could be asked to design a concept model of a new space shuttle that would be used for high-speed travel around the Earth using gravity, gravitational pull, and free fall for its path of flight. Students can then test their designs by dropping them from various heights, or even from the top of the school building, and time their descents and flight patterns as an evaluation of their aerodynamic efficiency.
Students can design art pieces, such as sculpture, that seem to defy gravity.
Students can cite specific sports where an athlete's actions seem to defy gravity and place them in a state of free fall.
Students can drop various items of different shapes and sizes and compare the time it took for them to fall to the Earth. This would allow them to understand that gravity is a constant unless something else acts upon the object, such as the atmosphere.
Students can explore formulas that deal with other aspects of motion. They can be encouraged to determine where these formulas apply to falling bodies, such as projectiles, and how to calculate the trajectory of a ballistic projectile.
Students can research various historical events that in some way were caused by the knowledge and understanding of gravity, gravitational pull, and free fall. Each student could select one event, write a one-page report on the event, and explain how gravity, gravitational pull, or free fall came into play.
The Art of Renaissance Science: Galileo Part I
Students can examine this site to get a historical perspective on how science evolved during the Renaissance. The primary focus is placed on Galileo and his accomplishments in science.
- Take a field trip to the Liberty Science Center or another nearby science museum. There are several hands-on exhibits and experiments that deal with gravity.
- There are twenty-eight NASA "Challenger Space Centers" located throughout the United States. If one is located near you, plan a field trip. Students will have an opportunity to participate in a simulated mission, learn the various jobs of an astronaut, and mission control personnel.
- Invite a certified scuba diver to your classroom to speak with your students on what it is like to work in an environment that is quite similar to outer space, in that even though they are in water, there is some correlation to working in a weightless environment.
- Visit a local amusement park. Have students examine and experience several different rides and explain which rides use gravitational pull, gravity, and free fall in their design.
- Invite an amusement park engineer into the classroom to discuss the role gravity plays in designing a ride or attraction.