Force and Motion Unit：力和运动单元.doc

Force, Motion, & Energy Transfer ModuleSummer 2006Pam Dixon, Allison Spencer,Sandie Spoon, & Kim BumpusModule OverviewFourth and fifth grade students will study how forces affect motion. This unit will provide hands-on learning activities that will help students fully understand the relationship between forces and motion.Module BackgroundForce is the push or pull applied to objects. Children witness “force” in many different situations everyday. Examples of force being applied to things are “pushing” the controls on a Game boy to play the game or just “clicking” the buttons on a remote control to see whats on television. These are obvious “forces” applied daily. There are “pushes” and “pulls” all around us that we dont see. Children need to be aware of these forces. Through a series of hands-on activities, our goal is to teach Newtons 3 Laws of motions which demonstrates “invisible” forces all around us. 1st Law: If no forces act on an object (or if the forces acting are balanced) then, if it is at rest, it will remain at rest, and if it is in motion, it will continue to move in a straight line path at a constant speed. 2nd Law: If a single force (or a combination of forces that is unbalanced) acts on an object, its speed and/or its direction will change. How quickly the speed (and/or direction) changes is directly related to the strength of the force and inversely related to the objects mass. 3rd Law: For every action, there is an equal and opposite reactionMissouri Grade Level ExpectationsStrand 2: Properties and Principles of Force and MotionBenchmark 2: Forces affect motionConcept D: Newtons Laws of Motion explain the interaction of mass and forces, and are used to predict changes in motiona. Recognize that balanced forces do not affect an objects motionb. Describe how unbalanced forces acting on an object changes its speed (faster/slower), direction of motion, or bothc. Explain how increasing or decreasing the amount of force on an object affects the motion of that objectd. Explain how mass of an object affects the force required to move ite. Predict how the change in speed of an object (faster, slower, remains the same) is affected by the amount of force applied to an object and the mass of the objectCommon Misconceptions Common Idea 2: Impetus Theory Force Runs OutThe moving objects force goes away and as a result the object gradually slows down and comes to a stop. In the physics classroom this often appears in statements such as “the force runs out.” Common Idea 4: Constant motion requires constant forcePeople often develop a general rule that an object moving at a constant speed must be experiencing a constant force. This idea is expressed in statements such as, “If it is moving, there must be some kind of push on it,” or “it is moving, it has to have some kind of force in it.” Lesson 1 How Force Affects MotionLesson 2 How Balanced Forces Affect MotionLesson 3 How Force is Affected by Speed and DirectionLesson 4 How Force is Affected by MassLesson 5 How Force is Affected by Speed and MassLesson 6 Friction Going, Going, Gone!Lesson 1MO Grade Level Expectations/Lesson Objectives: To explain how increasing or decreasing the amount of force on an object affects the motion of that objectGrade Level: 4th and 5th gradeTime Allotment: 50-60 minutesMaterials Needed: Low-friction cart, track, motion sensor connected to a computer, I&M computer simulatorElicitation: Imagine a soccer player about to kick a soccer ball lying in the grass. As their foot hits it, the ball begins to move. After the kick, the ball rolls across the grass and slowly comes to a stop. Draw on a piece of paper the movement of the ball. Be sure to show the balls movement while the players foot is touching it, and its movement after the foot no longer touches it. Please show in your picture where you think the foot is no longer touching the ball and explain your drawing.Why do you think the ball slows down and stops after it has been kicked?Now draw pictures of the ball and make arrows to show what forces (if any) you think are acting on the ball at two different times during its motion. Label your arrows to show to where the forces come from. 1) during the time the foot was touching the ball2) after the foot no longer touches the ball and it is rolling across the grass. Explain why you drew your pictures the way you did.Discuss your ideas with your team and try to agree on what the picture should look like. Draw your groups picture on a large piece of paper.Development: Experiment 1 “Motion Notion” (Is the motion of the cart after it has been pushed the same as during the push?)Step 1: Open the Motion Sensor data collection file for this experiment. Place your cart at rest on the track about 20-30 cm in front of the Motion Sensor. Start collecting Motion Sensor data and them have one of your team give the cart a quick push away from the sensor. (Stop the cart when it reaches the other end of the track.)Draw the speed-time graph for the motion of the cart. What happens to the speed of the cart while the hand is actually in contact with it? Does it speed up quickly, slow down quickly, or move at a reasonably constant speed?After the hand has lost contact with the cart does the behavior of the carts speed change, or does it continue moving in the same way as when your hand was in contact with it?Step 2: Return the cart to its starting position. Start collecting Motion Sensor data and then have one of your team members give the cart a gentle push away from the sensor with their hand. While the cart is moving, and before the data collection stops, give the cart two or three more pushes, in the same direction as the first push. (Stop the cart when it reaches the other end of the track.)Draw the speed-time graph for the motion of the cart. Each time the hand interacts with the cart, what happens to the carts speed? Does it speed up quickly, slow down quickly, or move at a reasonably constant speed?During the periods when the hand is not interacting with the cart what happens to the carts speed? (Is it increasing, decreasing, or fairly constant?) Does the cart move in the same way as when the hand is interacting with it, or is the speed behaving differently?What evidence would you look for to tell you a force is acting on the cart? To illustrate your thinking, use a colored pencil to indicate on the two speed=time graphs above the sections of the graph during which you think there is a force pushing the cart. Explain your reasoning below.Step 3: Three students are discussing the motion of the cart and the force acting on it. They all agree that while the hand is pushing it there is a force acting on the cart, but have different ideas about what happens during the periods, when the hand is not in contact with the cart. After the hand is removed there is no force on the cart. Thats why it moves differently.The force of the hand stops when contact is lost, but some other force must take over to keep the cart moving.The force of the hand is transferred to the cart and carried with. Thats why the cart keeps moving after the push. Kim James HaleyDo you agree with Kim, James, or Haley, or with none of them? Explain why.Consensus: Have students discuss the above statements in their group, and then select one member to share the groups ideas with the class.Application: For homework, have students think of one situation in real life where increased or decrease force changes the motion of an object.Lesson 2MO Grade Level Expectations/Lesson Objectives: Recognize that balanced forces do not affect an objects motionGrade Level: 4th and 5th gradeTime Allotment: 60 minutesMaterials Needed:Elicitation: Pass out one Post-It note per student. The students are to explain what happens when the cart is forced (pushed) forward on the track by a finger. Pair the students in groups of 2-4 students for them to share and discuss their thinking. If students need to change or add to their thoughts, give them time to change their ideas written on the Post-It note. Pull the group together for a class discussion. Create a web graphic organizer on the board or on chart paper. Ask the students to share their thoughts from the Post-It notes. Add these explanations to the web graphic organizer. During the discussion, guide the students to understand that the reason the cart moves forward is because a force is pushing it forward because nothing is stopping it from moving forward. When guiding the students, ask them questions to help them understand and give you their prior knowledge about how balanced forces affect an objects motion, without telling them the reasoning.Development: Now that you have assessed their prior knowledge, it is time for them to conduct experiments to develop and/or deepen their current knowledge. Step One: Place the cart on the track. Each group member needs to give the cart a quick push. Discuss what happens; students record results on their lab sheet. Why did the cart move on the track? How did the force of the quick push affect the cart? If time allows, test these runs using the motion sensor to give the students a visual. Discuss the results of the graph.Step Two: Once the students have an understanding of the motion of the cart after a quick push, they are to mount the fan on top of the cart. Each group member needs to see what happens once the fan is turned on and the hands are released from the cart. Discuss what happens; students record results on their lab sheet. Why did the cart move on the track? How did the force of the quick push affect the motion of the cart? If time allows, test these runs using the motion sensor to give the students a visual. Discuss the results of the graph.Step Three: Now, the students are to predict what will happen if they place their finger on the opposite side of the cart, opposing the force of the fan. Once each student has predicted the outcome, perform the test. Discuss what happens; students record results on their lab sheet. Did the cart move? Explain the motion of the cart. What affected the motion of the cart? If time allows, use the motion sensor. Discuss the results of the graph. Consensus: Group the students into small groups (3-4 students), if they arent already. Give them time to draw their observations in the space provided and answer the summarizing questions. Assess their current understanding as they work with their peers. Notice whether or not there are still some misconceptions. If so, either conduct the activities again or meet individually with these students to clear up the misunderstandings. When the groups have finished their drawings and summarizing questions, discuss the concepts learned. Application: Now that the students have learned the when forces are balanced, an object motion is not affected, it is time to relate this to a real-life situation. Facilitate a discussion how they can apply this concept to problem solve. If the students have difficulty thinking of ways, give them time to think about this overnight. Their homework assignment is to finish the last problem. Lesson 3MO Grade Level Expectations/Lesson Objectives: Describe how unbalanced forces acting on an object changes its speed (faster, slower, remain the same) direction of motion, or bothGrade Level: 4th and 5th gradeTime Allotment: 50-60 minutesMaterials: two carts, two fans, batteries 8 AA, motion sensor, cart track, colored pencils, graph, question page for Lesson 3Elicitation: What do you think would happen if two carts had two fans so that they push in opposite directions? Explain your thoughts. Predict the speed and time on the graph. Development: 1. Place the cart in the middle of the track. Place two batteries in one fan and three batteries in the other fan. Turn both fans on while one student is holding the cart. Let go of the cart. Practice this several times to get the feel of the cart. Dont let the cart fall off the track.a. How did the cart move faster, slower, or constant strength force (remain the same)? Explain your reasoning. b. Graph your findings. 2. Open the Motion Sensor data collection file for this activity. Place the cart in the middle of the track. Turn both fans on while one student is holding the cart. Let go of the cart a. Graph your results with a different color.b. What does the graph tell you about the movement of the cart?c. Was your prediction the same? Did the cart go faster, slower, or have a constant strength force (remain the same)?3. Next, place the cart in the middle of the track. Place two batteries in one fan and four batteries in the other fan. Predict what the cart will do. Turn both fans on while one student is holding the cart. Let go of the cart. Practice this several times to get the feel of the cart. Dont let the cart fall off the track.a. How did the cart move faster, slower, or constant strength force (remain the same)? Explain your reasoning. b. Graph your findings. 4. Open the Motion Sensor data collection file for this activity. Place the cart in the middle of the track. Turn both fans on while one student is holding the cart. Let go of the cart a. Graph your results with a different color.b. What does the graph tell you about the movement of the cart?c. Was your prediction the same? Did the cart go faster, slower, or have a constant strength force (remain the same)?Consensus:1. What was the motion of the cart like after letting go? Why did it act in that way?2. Comparing the two final graphs, what is similar about the speed on the graph?3. Comparing the two final graphs what is different about the speed on the graph? Explain what happened.Application:Simulator Exploration What effect does an unbalanced combination of forces have on an object that is already moving? Open the simulator for Cycle 2, Activity 3, Homework 1. Predict which cart will finish first. Watch the simulator speed arrows above each cart. What difference do you see? Why? Are there unbalanced forces working in this simulation? How did your prediction look against the simulation?Lesson 3 questions Explain all questions with compete sentences, using Science vocabulary.Question 1 a. How did the cart move faster, slower, or constant strength force (remain the same)? Explain your reasoning. b. Graph your findings.Question 2 a. What does the graph tell you about the movement of the cart?b. Graph your results with a different color.c. Was your prediction the same? Did the cart go faster, slower, or have a constant strength force (remain the same)?Question 3 a. How did the cart move faster, slower, or constant strength force (remain the same)? Explain your reasoning. b. Graph your findings.Question 4 a. What does the graph tell you about the movement of the cart?b. Graph your results with a different color.c. Was your prediction the same? Did the cart go faster, slower, or have a constant strength force (remain the same)?Consensus questions1. What was the motion of the cart like after letting go? Why did it act in that way?2. Comparing the two final graphs, what is similar about the speed on the graph?3. Comparing the two final graphs what is different about the speed on the graph? Application questions 1. Comparing the graphs, what differences do you see? Why? 2. Are there unbalanced forces working in this simulation? 3. How did your prediction look against the simulation?Lesson 4MO Grade Level Expectations/Lesson Objectives: Explain how the mass of an object (e.g. cars, marbles, rocks, boulders) affects the force required to move itGrade Level: 4th and 5th gradeTime Allotment: 50-60 minutesMaterials: two carts, motion sensor, cart track, colored pencils, graph, question page for Lesson 4Elicitation:What would happen if we put a one pound rock on top of the cart? Would the new mass (weight) change the speed? Would the direction change? Predict the movement of the cart on the graph.Development:1. Set the track out on level ground. Set the motion sensor on one end of the track. Plug in the sensor to the computer. 2. Place the cart 20-30 cm from the motion sensor. Practice pushing the cart with an easy push. Practice this several times. Predict the speed and time on the graph. Next use the motion sensor to collect the data for speed and time. Graph the resultsa. Did the movement follow your prediction? Explain your reasoning. 3. With the cart on the track, place the one pound rock on top of the cart. Place the cart 20-30 cm from the motion sensor. Predict what the graph will look like. Do an easy push on the cart. Next, use the motion sensor to collect the data for speed and time. Using a different color, graph the results.a. Did the movement follow your prediction?b. Did the cart move slower, faster, or have a constant strength force (remain the same)?c. Does mass make a difference? Why?d. Is there a difference if you start at the other end of the track?e. What would happen if the mass was 5 pound?Consensus:1. Compare the last two graphs. 2. How did the graphs change? 3. What proof or evidence do yo