E Physics: A. Newton s Three Laws of Motion Activity: Rocketry Appendix A: Straw Rocket

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1 Appendix A Note: Do not begin this appendix until you have reached step 7 of the parent lesson, Rocketry. Note: This lesson contains two launch options: Launch Option 1 uses a less formal analysis of launch data as it pertains to Newton s Second Law of Motion; Launch Option 2 uses a formal approach of launch data analysis, requiring the students to take measurements and recordings. Choose one option or the other. Both will allow for an understanding of Newton s Second Law of Motion. If you choose Launch Option 2, you must also complete the lesson Data Analysis: Rocket Launch. Prerequisite: Rocketry Parent Lesson Time: Minutes Instructor Materials: Pitsco Dr. Zoon Straw Rocket Video (optional, but recommended) Projection system for video (optional) Student Materials: Pitsco straw rocket launcher (number depends on class size, recommend 4 per class) Pitsco Straw Rocket Class Pack (1 per class) Included in each class pack:»» 100 precision straws»» x 5 index cards»» Pound of modeling clay (not needed for lesson) Chisel-tip pencil eraser (2 or 3 per rocket) Transparent tape (optional, recommend 1 roll per 4 students) Masking tape (optional, recommend 1 roll per 4 students) Scissors (optional, recommend 1 per student) Metric ruler (recommend 1 per student) Straw Rocket Construction sheet (optional, recommend 1 per student) Safety goggles Additional Materials for Launch Option 2: 30-meter wind-up tape measure (recommended 1 per launcher) Digital scale (recommend 1 per group of 2 to 4 students) 1

2 Instructor Background Information: Action/Reaction The liftoff of the straw rocket demonstrates Newton s Third Law: for every action there is an equal and opposite reaction. When raising the mass rod to a set height and dropping it, the rod exerts a force on the piston (or air chamber ), compressing the air in the piston chamber. The mass of pressurized air rapidly escapes the chamber, exiting through the end of the brass launch tube. With the straw rocket inserted over the brass launch tube, the rushing mass of air gives a propelling moment that results in flight. The launcher absorbs the reaction to this rapid discharge of air. Because the launcher is relatively heavy and resting on a solid surface (i.e., the floor or table), the reactive force during liftoff is insufficient to overcome the weight and friction of the launcher. If the launcher was mounted in a fashion that made it weightless and frictionless, the launcher would have a visible reaction to the release of the air charge. It would travel in a direction opposite of the rocket. As an example, we can observe a similar reaction when firing a rifle, it kicks (recoils) in a direction opposite of the bullet. Mass rod raised and then dropped Air exits brass launch tube, propelling rocket forward 2

3 Instructor Preparation: Note: You may preconstruct rockets for the students if time is a concern. Setup and Implementation üü üü If desired, make enough copies of the Straw Rocket Construction sheet so each student in your class has a copy. The sheet provides basic assembly instructions. During construction, you may want to allow the students to experiment with different fin designs and placement, number of fins, and rocket body length. For each rocket, the students will need the following materials 1 precision straw 1 3 x 5 index card Several pieces of transparent tape A short length of masking tape 2 to 3 chisel-tip pencil erasers Tools (ruler, scissors, pencil) may be shared by students Launching the Rockets üü üü To launch the straw rockets, use the Pitsco Straw Rocket Launcher. You will find it is extremely easy to operate. Carefully follow the launch directions included with the launcher. Read the Straw Rocket Safety section and make sure that students follow the safety rules. Since the rockets can launch as far as 50 feet in some cases, it is recommended for use in a large, open indoor area, such as a gymnasium. Before beginning this activity with the students, you will want to predetermine launch angle and force for each of the launches you will conduct. Familiarize yourself with the two launch options (pages 5-6 and 9-10). If doing Launch Option 1, using less formal data analysis, you will likely need to vary the force significantly so it is easily discernible that the greater force, when applied to rockets of equal mass, will launch the rocket a greater distance. Likewise, when launching with mass as a variable and force as a constant, you will want to ensure their is a sufficient variation in mass so the students can easily see that the rocket with greater mass will not launch as far as the rocket with less mass. 3

4 üü If you are choosing to conduct Launch Option 2, which uses formal data analysis, you may not need to exaggerate the variations in force and mass as you do for Launch Option 1. Launch Option 2 uses a tape measure to more accurately measure data. 4

5 Lesson: Note: To save time with fins, you can construct them from two pieces of 1 x 2 cardstock. Place the two pieces together and staple them about 0.75 from each end. Using a pencil point, slightly separate the two pieces and insert the opening at the tail end of the straw. Secure the fins in place with a small strip of transparent tape, being careful not to tape over the straw opening. Fins made from stapled cardstock Note: When conducting Launch Option 1 (the less formal approach to Newton s Second Law), it is unnecessary to mass the rockets because it is evident the mass increases as one adds a second eraser. Rocket Construction 1. Have students construct their rockets, following the Straw Rocket Construction sheet or, if you prefer, guide the students through the construction process, using a demonstration method. If you have pre-constructed rockets for the students, skip this step and go directly to step 2. Choose a Launch Option 2. There are two launch options with the lesson. Launch Option 1 uses a less formal approach that correlates to Newton s Second Law of Motion. Launch Option 2 uses a formal approach, which requires students to take specific measurements and record their findings on their activity log. Additionally, if doing Launch Option 2, the students must also complete the lesson Data Analysis: Rocket Launch. Choose your preferred option and follow the appropriate steps. Note that there are also two variations of the activity log, each applicable to the appropriate launch option. Safety 3. Review all launch safety procedures with the students before conducting any rocket launch. When commencing the rocket launch, everyone must wear safety goggles. Never walk in the path of a launching rocket. Do not run when retrieving your rocket. Launch Option 1 Launch: Mass as Variable A. In their activity log, have students predict how increasing the mass with each launch, while applying the same force, will affect the rocket s range. B. Have the students set the launch angle to the value you predetermined during Instructor Preparation on page 3. Inform the students of the launching forces as predetermined from Instructor Preparation. Explain to the students that they should not change the angle or force for each launch these values are constants. 5

6 C. Have the students conduct two launches, the first launch with one eraser fitted to the nose, and the second launch with two or three erasers fitted to the nose. (The number of erasers used should have been determined during Instructor Preparation.) D. Ask: Which rocket traveled further, the rocket with less mass or more mass? Why? (The students should recognize that the rocket with less mass traveled further because it had greater acceleration than the rocket with more mass.) Relate this to Newton s Second Law of Motion. Launch: Force as Variable E. Using their activity log for recording, ask for the students to predict how increasing the force for each launch, while keeping the mass constant, will affect the rocket s range. F. Have the students set the launch angle to the value you predetermined during Instructor Preparation on page 21. Also, inform the students of the launching force they will apply to each launch. (You should have predetermined the forces during Instructor Preparation.) Inform the students that they should not change the angle or mass for each launch these values are constants. Erasers affixed to nose Note: If you and your students want additional references for building and launching straw rockets, refer to the Dr. Zoon Straw Rockets Video (#59240). G. Have the students conduct two launches, each with a different amount of force. H. Ask: Which rocket traveled further, the rocket that had less force applied to it or the rocket that had more force applied to it? (The students should recognize that the rocket that had more force applied to it traveled further. It had greater acceleration.) Relate this to Newton s Second Law of Motion. I. With the launches concluded, return to page 13, step 8, in the parent lesson. 6

7 Straw Rocket (Launch Option 1) Activity Log Launch: Mass as Variable 1. If applying the same force to two rockets, which rocket will travel further? the rocket with more mass the rocket with less mass Outcome 2. The rocket with more mass less mass traveled further because Launch: Force as Variable 3. If two rockets of the same mass launch but one has more force applied to it, which rocket will travel further? the rocket with more force the rocket with less force Outcome 4. The rocket with more force less force traveled further because

8 Straw Rocket (Launch Option 1) Activity Log Launch: Mass as Variable 1. If applying the same force to two rockets, which rocket will travel further? the rocket with more mass the rocket with less mass Outcome 2. The rocket with more mass less mass traveled further because the rocket with less mass had greater acceleration. Launch: Force as Variable 3. If two rockets of the same mass launch but one has more force applied to it, which rocket will travel further? the rocket with more force the rocket with less force Outcome 4. The rocket with more force less force traveled further because the rocket with more force had greater acceleration. 8

9 Launch Option 2 Mass the Rockets A. Once the students complete construction have them measure the mass of their rocket, recording their findings on the activity log page. Measuring Mass Procedures Find the mass of the entire rocket with one pencil eraser fitted over the end. Record result. Fit a second eraser over the first eraser and record the mass. If time permits, you may have the students mass a third eraser. Launch: Mass as Variable B. In their activity log, have students predict how increasing the mass with each launch, while applying the same force, will affect the rocket s range. C. Have the students set the launch angle to the value you predetermined during Instructor Preparation on page 3. Inform the students of the launching force as predetermined from the Instructor Preparation. Inform the students that they should not change the angle or force for each launch these values are constants. D. Have the students conduct two launches, the first launch with one eraser affixed to the nose, and the second launch with two erasers affixed to the nose. (You may have them conduct a third launch, with the third eraser, if time is available.) Using the tape measure, the students should measure the distance traveled for each launch, recording the findings in the activity log table. Launch: Force as Variable E. Using their activity log for recording, ask for the students to predict how increasing the force for each launch, while keeping the mass constant, will affect the rocket s range. 9

10 F. Have the students set the launch angle to the value you predetermined during Instructor Preparation on page 2. Also, inform the students of the launching forces they will apply to each launch. (You should have predetermined the forces during Instructor Preparation.) Inform the students that they should not change the angle or mass for each launch these values are constants. G. Have the students conduct two launches, each launch with a different degree of force. (You may have them conduct a third launch, with a third force variable, if time is available.) Using the tape measure, the students should measure the distance traveled for each launch, recording the findings in the activity log table. H. Complete the lesson Data Analysis: Rocket Launch. Once complete, return to the rocketry parent lesson, page 13, step 8. 10

11 Straw Rocket (Launch Option 2) Activity Log Launch: Mass as Variable 1. As I increase the amount of mass on the rocket but keep the applied force the same, the rocket will travel a longer distance travel a shorter distance Mass of Rocket Force Applied Launch Angle Distance Traveled Launch 1 Launch 2 Launch 3 (optional) Launch: Force as Variable 1. As I increase the amount of force on the rocket but keep the mass the same, the rocket will travel a longer distance travel a shorter distance Mass of Rocket Force Applied Launch Angle Distance Traveled Launch 1 Launch 2 Launch 3 (optional)

12 Straw Rocket (Launch Option 2) Activity Log Launch: Mass as Variable 1. As I increase the amount of mass on the rocket but keep the applied force the same, the rocket will travel a longer distance travel a shorter distance Mass of Rocket Force Applied Launch Angle Distance Traveled Launch g m Launch g m Launch 3 (optional) Launch: Force as Variable 1. As I increase the amount of force on the rocket but keep the mass the same, the rocket will travel a longer distance travel a shorter distance Mass of Rocket Force Applied Launch Angle Distance Traveled Launch g m Launch g m Launch 3 (optional)

13 Straw Rocket Construction 1. Design a rocket: Determine what fin shape, number of fins, and rocket length you want. There are some suggested fin designs in the diagram below, but you are not limited to these suggestions. Fin Shape Samples 2. Draw your chosen fin shape on an index card, drawing as many fins as you wish to place on your rocket (usually two to four fins per rocket). 3. Cut out the fins. 4. Cut the straw to the desired length. (The straw serves as the rocket body.) 5. Cut a piece of tape that is long as the edge of the fin which is to be connected to the rocket body. Place the tape on the edge of one fin. Repeat this for all the fins. Attach the fins so they are evenly spaced around the straw. Carefully trim off any excess tape. 6. Add masking tape to the top of the rocket (the end opposite the fins), wrapping it around the straw. Add enough tape so the pencil eraser fits snuggly; the eraser should not slip off easily. Finished Rocket Your rocket is done!