Activity: Newton s Third Law of Motion Action and Reaction

Transcription

1 Ascent to Orbit Activity: Newton s Third Law of Motion Action and Reaction Background Information for the Teacher: Adapted from www. nasa.gov, and Isaac Newton s three laws of motion and the law of gravity that explain motions are observed on Earth and in space. In the case of rockets, the action is the force produced by the expulsion of gas, smoke and flames from the nozzle end of a rocket engine. The reaction force propels the rocket in the opposite direction. Newton s laws of motion explain just about everything you need to know about rockets. Newton s third law deals with actions and reactions. Stated simply, the law says that "for every action, there is an equal and opposite reaction." The statement of this law is deceptively easy. However, the key to grasping this law correctly is to understand Credit: National Air and Space Museum, Smithsonian Institute action-reaction pairs. Pair means two, so only two objects are in an action-reaction pair. Action is the result of a force. Release air from an inflated balloon. The air shoots out the nozzle. That is an action. Reaction is related to action. When the air rushes out of the balloon, the balloon shoots the other way reaction! What causes action and reaction to occur? The action and reaction in Newton's third law are forces. If you recall from our previous lessons, force was defined as a push or pull on an object. To take this concept further, you should also add that force is an agent of change. The application of a force to a body (one that is free to move) changes the body's state of motion, that is, it changes its velocity (the speed of something in a given direction). "If you insist upon a precise definition of force, you will never get it!" (Richard P. Feynman, Robert B. Leighton, and Matthew Sands, The Feynman Lectures on Physics, Addison-Wesley, Reading, MA, Vol. 1, 1964, p. 2 4). In the case of rockets, however, burning rocket propellants that expand explosively usually exerts force. Unbalanced force refers to the sum total or net force exerted on an object. The forces on a coffee cup sitting on desk, for example, are in balance. Gravity is exerting a downward force on the cup. At the same time, the structure of the desk exerts an upward force, preventing the cup from falling. The forces are in balance. Reach over and pick up the cup. In doing so, you unbalance the forces on the cup. The weight you feel is the force of gravity acting on the mass of the cup. To move the cup upward you have to exert a force greater than the force of gravity and the muscle force you are exerting are in balance.

2 Background Information for the Teacher, Continued Let s look at an example of Newton s action-reaction law: The Sun s gravitational force acting on Earth is an action and the Earth's gravitational force acting on the Sun would be considered a reaction. Earth's gravitational force on the Sun and the Sun's gravitational force on Earth is an action-reaction pair. Gravity is the force holding the universe together. There is a gravitational force between any two objects in the universe, so it is called universal gravitation. Gravity pulls you down because there is a gravitational force between you and the earth as well as between you and the Sun and even, between you and the person sitting next to you. You don t fall to the sun because it is too far way for its gravitational force to be strong. You don t fall toward the people sitting next to you because they are less massive than Earth. What happens when you're standing still on a skateboard and then suddenly step off? The force of stepping off the board pushes your skateboard (and you) in the other direction. The same force occurs when you step off a boat onto a pier. Unless the boat is held in some way, it moves in the opposite direction. You can also demonstrate this using Newton s Cradle. This apparatus consists of steel balls suspended on a frame. When the ball on one end is pulled back and then let go, it swings into the other balls. The ball on the opposite end then swings up with an equal force to the first ball, as shown in the illustration on the right. The force of the first ball causes an equal and opposite reaction in the ball at the other end. Fun Fact: Action/reaction force pairs also make it possible for birds to fly. The wings of a bird push air downward (action). In turn, the air pushes the bird upward with an equal force (reaction).

3 Activity Overview: Students construct a rocket from a balloon propelled along a guide string. They use this model to learn about Newton's Third Law of Motion, examining the effect of different forces on the motion of the rocket. Learning Objective: Students will demonstrate practical applications of Newton's Laws of Motion by using the model of the balloon to understand the different forces that act on the rocket. They will also collect data from the experiment and graph the results. Science Process Skills: Observing, Measuring, Predicting, and Investigating Estimated Time Required: Day 1 =50 minutes, Day 2 =50 minutes Teacher Preparation: Make sure you have all the materials ready for your students in advance. Assemble students in teams of four Choose appropriate locations for students to set up the experiment Technology Give each Activity= team the listed materials and the Data Sheets Technology Activity= Newton s Laws App, Isaac Newton App, Newton App Materials: Plastic Drinking Straw Tape Ruler Fishing line or smooth string Long, tube-shaped balloon Skateboard Basketball Data Sheets Literature Book: TECHNOLOGY: How today's technology really works by Clive Gifford Literature Book: Isaac Newton s Laws of Motion by Andrea Gianopoulos What You Do! 1. [Day 1] Engage students by asking them the following question: o What happens when you fill a balloon with air and then release it? How does the balloon move? o Has anyone ever stepped forward off a skateboard suddenly? What happened? o What do you think happens if a person were to step off a boat onto a pier? In which direction does the boat seem to move? Brainstorm student answers on the board. Keep these ideas on the board during the class period so you can refer back to them as you learn more about rockets and how they work. Science Vocabulary Action-Reaction Force Gravity Newton s Cradle Mass Unbalance Force Universal Gravitation Velocity

4 What You Do! Continued 2. Start with an in-class demonstration. Have a student stand on a skateboard and throw a basketball. Invite the class to observe what happens (note: this could be dangerous; be very careful not to have the student fall). The student rolls backwards on the skateboard. Allow students time to observe and respond to the demonstration. Invite them to speculate the conditions if the skateboard were larger or smaller, or if the basketball were bigger and/or heavier, smaller and/or lighter, or if the floor were smoother/rougher. What would be the outcome? 3. Remind students that our purpose for observing this third law of motion today is mainly to understand that the motion of objects on Earth also apply to the motion of objects in Space. Our understanding of how rockets work arises from Sir Isaac Newton s three laws of motion. It is important for engineers to understand Newton s laws because they not only describe how rockets work they explain how everything that moves or stays still works! Tell students that this activity demonstrates all three of Newton s laws of motion. The focus of the activity is Newton s third law of motion, but the first and second laws are intrinsically involved with the motion of the rocket as well. 4. TechConnect= Connect your ipad Mini to the projector so the students can watch a YouTube video called Newton s 3 rd Law of Motion. Have them scroll down to the video uploaded by MacMillanSpaceCenter. Have students discuss what they observed from the action-reaction experiment as soon as they are done watching the video. Then bring the whole class back together for a discussion on Newton s Third Law. 5. Make copies of pages in the literature book-technology: How today's technology really works by Clive Gifford. Students will be able to read about rocket propulsion and see a few pictures of how Lift Off! has changed over time. 6. [Day 2] Tell students that they are going to complete an experiment similar to the one they saw on YouTube. However, a chemical compound will not be used, just simply air and a balloon. Invite students to think about why they should perform this experiment and how it relates to their understanding of physics. 7. Gather materials for this activity. Choose appropriate locations for students to set up the experiment. 8. Assemble students into teams of four to six. Make sure all teams have the listed materials. Allow teams to complete the activity a number of times while they observe and write a brief description of the experiment. Students should also use the ipad Mini to video the action reaction activity. You may want to designate roles for students such as tester, recorder, videographer and presenter. Make sure the videographer uses the ipad Mini to capture this experiment in the making. It could make for some funny footage!

5 What You Do! Continued 9. Show your students the handout Newton s Third Law. Have them complete the written exercise. In this exercise, students will learn why action reaction forces occur. Remind them that these forces come in pairs. You may want to read the directions aloud while students follow along. 10. TechConnect: Have students click on the ipad Mini app called Newton s Laws. Students can click to learn about Newton s Third Law of Physics. Feel free to use this app as it was initially introduced in the first law of motion activity. It is a good way to reinforce learned concepts. Checking For Understanding! While students are working on their experiments, walk around the room and them to give verbal descriptions of Newton s Third Law. If students can tell you that air pushing is an action and the balloon pushing back is a reaction, then they understand the concept. Modifications For Older Students: To ensure that your students are receiving a sufficient challenge from this lesson, have them expand their visual skills by making a plot showing the distance that the balloon travelled with different air volumes. This can be one on graph paper or with a computer software package like Microsoft Excel). For Younger Students: To ensure that your students are learning at the appropriate level, you may want to briefly review fractions in a visual way: ½, ¼ ¾. Reviewing this may help them understand how much air to fill in the balloon experiment. TechConnect: A great enrichment activity for the lessons on Newton s Laws is to have the students use two ipad Mini apps: Newton and Isaac Newton. These apps give an overview of the life of Isaac Newton in a story form. The app, Newton, is a better choice for less advanced students because it reads like a storybook. The other app, Isaac Newton, would be better for more advanced students. Both apps are very informative and span through Isaac Newton s life and give information about his achievements. Students could use these apps to write a report about Isaac Newton or create a comic book about him, like the book, Isaac Newton s Laws of Motion by Andrea Gianopoulos.

6 Ascent to Orbit Newton s Third Law: Part 1: The History Action of Space Travel - Reaction What You Do! Continued Action and Reaction A rocket can liftoff from a launch pad only when it expels gas out of rom launching to Students will record its how engine. high The their rocket pushes flew and on change the gas, in and distance the gas, from in turn, launching pushes to ce, make 2 large landing on their data on sheet. the rocket. Once all The students whole process have tested is very their similar rocket to once, riding make a 2 large et will represent data tables on the skateboard. so students Imagine can share that a their skateboard results. and One rider data are sheet in a will state represent of rest ata sheet will Rocket Propulsion and (not will moving). show how The rider high pushes the rocket off flew. the skateboard. The other data In the sheet third will law of d from launch represent Rocket Stability motion, and the will stepping show off how is much called distance action. is The measured skateboard from launch responds and landing. Discuss to the that results action as by a traveling class. some distance in the opposite direction. The Sample Questions: skateboard's motion is called a reaction. When the distance traveled er? by the rider and the skateboard o How are stable compared, were the it class would rockets appear when that the compared skateboard to one has another? had a much greater reaction than the action o of the Was rider. there This much is not variance the case. in how The high reason the the rocket skateboard flew? has traveled farther is that it has less mass than the o rider. What could explain discrepancies in the data? eir rocket flight TechConnect: Have your students use the ipad Mini to take video of their rocket flight ey want With to rockets, the action or take is pictures the expulsion of their of experiment gas out of the in progress. engine. The They reaction can choose is the how movement they want of the to rocket in the opposite direction. digitally To document enable a rocket their experiment. to lift off from the launch pad, the action, or thrust, from the engine must be greater than the weight of the rocket. In the microgravity environment of Earth orbit, e following 6. Now, allow your students time to design their own experiment to test the following however, even tiny thrusts will cause the rocket to change direction tudents can only question: How do we make a paper rocket fly in the most stable way? Students can only e paper used to change one variable in their experiment. They can change: 1. Type of the paper used to A rocket, in its simplest form, is a chamber enclosing a gas under pressure. A small opening at one end of the ion of pennies to create the rocket 2. Shape, size, or number of fins on the rocket 3. Addition of pennies to chamber allows the gas to escape, and, in so doing, provides a thrust that propels the rocket in the opposite o test a different add weight to the rocket. 4. Length of the rocket. If your students want to test a different direction. A good example of this is a balloon. roval first. Once variable to see if it affects the rocket s stability, have them get your approval first. Once e to create their students have decided what variable they are going to test, give them time to create their The balloon s rubber walls compress air inside a ksheets while rockets, test them out, and gather results. Students will fill out their worksheets while balloon. The air pushes back so that the inward and e and create a completing the inquiry experiment. Have students fill out their data table and create a outward forces are balanced. When the nozzle is ested the same graph to represent their findings. Then, match groups up together who tested the same released, air escapes and the forces become unbalanced. verall results variable change and have them share results. Students will then graph overall results The action of the escaping gas propels the balloon in a udents answer the based on their results in addition to other groups results. Lastly, have students answer the rocket flight. The balloon's flight is highly erratic conclusion questions to expand upon their findings. because it has no structures, such as fins, to stabilize it. When we think of rockets, we rarely think of balloons. eir rocket flight TechConnect: Have your students use the ipad Mini to take video of their rocket flight Instead, our attention is drawn to the giant vehicles that carry satellites into orbit and spacecraft to the Moon and planets. cient challenge above are part Activity 4: Exploring Rockets Directions: Read the information below. Answer the questions that follow about this article. Modifications: For Older Students: To ensure that your students are receiving a sufficient challenge from this lesson, make sure that Step 3 and Step 6 in the What You Do above are part of how you present your lesson. Space space. arly wn 5 TechConnect: For additional enrichment, have students use the Man in Space App on the ipad Mini to read about the First Steps towards getting to space. Included in this app is information about the first rocket designers, the early satellites sent to space, and the first man in space. Students can write down 5 facts that they learned from reading each article.

7 Ascent to Orbit Newton s Third Law: Part 1: The History of Action Space Travel - Reaction Activity 4: Exploring Rockets Directions: Answer the questions below based on the article called: Newton s Third Law: Action-Reaction. What You Do! Continued 1. What does Newton s Third Law of Motion state? from launching to Students will record how high their rocket flew and change in distance from launching to nce, make 2 large landing on their data sheet. Once all students have tested their rocket once, make 2 large heet will represent data tables on the board so students can share their results. One data sheet will represent data sheet 2. will If a skateboarder Rocket is Propulsion stepping off and of will a skateboard show how and high this the motion rocket of flew. stepping The other forward data off sheet the will skateboard red from launch causes the skateboard represent Rocket to roll Stability backwards, and what will show is the how action much in this distance scenario? is measured What is the from reaction? launch and landing. Discuss the results as a class. Sample Questions: ther? o How stable were the class rockets when compared to one another? o Was there much variance in how high the rocket flew? o What could explain discrepancies in the data? their rocket flight TechConnect: Have your students use the ipad Mini to take video of their rocket flight they want 3. to Think about or it! take Would pictures the of weight their of experiment the rider have in progress. any effect They on can this choose action/reaction how they principle? want to Explain your thoughts. the following 6. Now, allow your students time to design their own experiment to test the following Students can only question: How do we make a paper rocket fly in the most stable way? Students can only the paper used to change one variable in their experiment. They can change: 1. Type of the paper used to ition of 4. pennies Let s to apply create the action-reaction the rocket 2. Shape, idea to size, the Space or number Shuttle. of fins In the on picture the rocket below, 3. Addition label the of action pennies and to t to test a different reaction occurring add weight as the to the Space rocket. Shuttle 4. Length is launched. of the rocket. If your students want to test a different proval first. Once variable to see if it affects the rocket s stability, have them get your approval first. Once ime to create their students have decided what variable they are going to test, give them time to create their orksheets while rockets, test them out, and gather results. Students will fill out their worksheets while ble and create a completing the inquiry experiment. Have students fill out their data table and create a tested the same graph to represent their findings. Then, match groups up together who tested the same overall results variable change and have them share results. Students will then graph overall results students answer the based on their results in addition to other groups results. Lastly, have students answer the conclusion questions to expand upon their findings. their rocket flight th TechConnect: Have your students use the ipad Mini to take video of their rocket flight Modifications: ficient challenge For Older Students: To ensure that your students are receiving a sufficient challenge o above 5. are part Balloons can from be this very lesson, similar make to rockets sure that when Step it comes 3 and Step to the 6 principle in the What of action-reaction. You Do above Label are part the action and of reaction how you on the present balloon your below. lesson. in Space o space. early own 5 TechConnect: For additional enrichment, have students use the Man in Space App on the ipad Mini to read about the First Steps towards getting to space. Included in this app is information about the first rocket designers, the early satellites sent to space, and the first man in space. Students can write down 5 facts that they learned from reading each article.

8 Ascent to Orbit Newton s Third Law: Part 1: The History of Action Space Travel - Reaction Activity 4: Exploring Rockets Data Sheet rom launching to Students will record how high their rocket flew and change in distance from launching to ce, make Team 2 large Name landing on their data sheet. Once all students have tested their rocket once, make 2 large et will represent data tables on the board so students can share their results. One data sheet will represent ata sheet Directions: will Read Rocket the information Propulsion below. and will Complete show how the experiment high the rocket and record flew. The your other data data then sheet answer will the d from launch following question. represent Rocket Stability and will show how much distance is measured from launch and landing. Discuss the results as a class. Procedure: Sample Questions: er? 1. With pieces of o string How cut stable to fit were around the the class balloon, rockets measure when compared the circumference to one another? of balloon with different amounts o Was of air there in it much (completely variance full, in how ¼ full, high ½ full, the rocket and ¾ flew? full) and record the circumference in the table shown o What below. could explain discrepancies in the data? eir rocket flight 2. Set aside the TechConnect: pieces of string. Have your students use the ipad Mini to take video of their rocket flight 3. Slide the drinking or take pictures straw onto of their a piece experiment of string. in progress. They can choose how th 4. Choose two people from your team to hold each end of the string taut and level. Place two loops of e following masking 6. tape Now, onto allow the your straw. students time to design their own experiment to test the following tudents can 5. only Blow up the question: balloon How to its do maximum we make capacity a paper rocket (greatest fly volume). in the most Hold stable tightly way? onto Students the neck can of only the e paper used to balloon so change that no one air escapes, variable and in their attach experiment. the balloon They to the can two change: pieces 1. of Type tape. of The the neck paper of used the to ion of pennies to create the rocket 2. Shape, size, or number of fins on the rocket 3. Addition of pennies to balloon should be parallel to the string. o test a different add weight to the rocket. 4. Length of the rocket. If your students want to test a different roval first. Once 6. Release the variable neck to to let see the if air it affects rush out the of rocket s the balloon. stability, have them get your approval first. Once e to create 7. their In the table students shown have below, decided record what (a) the variable distance they that are the going balloon to test, traveled give them (as marked time to on create the string) their ksheets while and (b) the rockets, amount test of them air in out, the balloon. and gather results. Students will fill out their worksheets while e and create 8. a Repeat steps completing 4-7 above, the filling inquiry the experiment. balloon with Have different students amounts fill out of their air. data Use the table pieces and create of string a you ested the same measured graph in Step to one. represent their findings. Then, match groups up together who tested the same verall results variable change and have them share results. Students will then graph overall results udents answer Analyze the Data: Complete based on their following results in table. addition to other groups results. Lastly, have students answer the conclusion questions to expand upon their findings. Amount of Circumference Diameter Distance Traveled (cm) eir rocket flight Air TechConnect: (cm) Have your students (cm) use the ipad Mini to take video of their rocket flight Full cient challenge above are part Space space. arly wn 5 Adapted from Action Reaction Activity NASA Quest What You Do! Continued Modifications: For Older Students: To ensure that your students are receiving a sufficient challenge ¼ Full from this lesson, make sure that Step 3 and Step 6 in the What You Do above are part of how you present your lesson. ½ Full TechConnect: For additional enrichment, have students use the Man in Space App on the ipad Mini to read about the First Steps towards getting to space. Included in this app is information about the first rocket designers, the early satellites sent to space, and the first man in space. Students can write down 5 ¾ Full facts that they learned from reading each article.

9 Ascent to Orbit Newton s Third Law: Part 1: The History Action of Space Travel - Reaction Activity 4: Exploring Rockets Data Sheet Questions Adapted from Action Reaction Activity NASA Quest What You Do! Continued Team Name rom launching to Students will record how high their rocket flew and change in distance from launching to ce, make 2 large landing on their data sheet. Once all students have tested their rocket once, make 2 large et will represent data tables on the board so students can share their results. One data sheet will represent What is the action force in this investigation? ata sheet will d from launch er? Rocket Propulsion and will show how high the rocket flew. The other data sheet will represent Rocket Stability and will show how much distance is measured from launch and landing. Discuss the results as a class. Sample Questions: o How stable were the class rockets when compared to one another? What is the reaction force in this investigation? eir rocket flight o Was there much variance in how high the rocket flew? o What could explain discrepancies in the data? TechConnect: Have your students use the ipad Mini to take video of their rocket flight Did the amount of air in the balloon change its speed? In what way? e following 6. Now, allow your students time to design their own experiment to test the following tudents can only question: How do we make a paper rocket fly in the most stable way? Students can only e paper used to change one variable in their experiment. They can change: 1. Type of the paper used to ion of pennies to create the rocket 2. Shape, size, or number of fins on the rocket 3. Addition of pennies to o test a Did different you experience any add challenges weight to the in setting rocket. up 4. Length and/or carrying of the rocket. out your If your experiment? students want Explain. to test a different roval first. Once variable to see if it affects the rocket s stability, have them get your approval first. Once e to create their students have decided what variable they are going to test, give them time to create their ksheets while rockets, test them out, and gather results. Students will fill out their worksheets while e and create a completing the inquiry experiment. Have students fill out their data table and create a ested the Think same about some other graph examples to represent of action their findings. reaction Then, forces match you might groups have up together seen or experienced. who tested the List same those verall results below and draw a picture. variable change and have them share results. Students will then graph overall results udents answer the based on their results in addition to other groups results. Lastly, have students answer the conclusion questions to expand upon their findings. eir rocket flight cient challenge above are part Space space. arly wn 5 TechConnect: Have your students use the ipad Mini to take video of their rocket flight Modifications: For Older Students: To ensure that your students are receiving a sufficient challenge from this lesson, make sure that Step 3 and Step 6 in the What You Do above are part of how you present your lesson. TechConnect: For additional enrichment, have students use the Man in Space App on the ipad Mini to read about the First Steps towards getting to space. Included in this app is information about the first rocket designers, the early satellites sent to space, and the first man in space. Students can write down 5 facts that they learned from reading each article.