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TEACHER’S GUIDE OBJECTIVES Students should be able to

» list the variables that affect projectile motion.

» list the variables that do not affect projectile motion.

» create an optimal design for a projectile by using the design, test, and redesign engineering process.

» use knowledge of projectile motion to solve real-world problems.

EQUIPMENT

(Dimensions of wood pieces are suggestions and may vary)

» 18” 1x4 for the base

» 5” 1x6 for the launch angle guide

» 24 in. 3/4 square dowel (for the launch rail)

» 2 in. #10 wood screws (2)

» 2 in. #10 bolt, wingnut, and washer (If bought separately, be sure the bolt and wingnut have threads of the same pitch such as #10– 24 x 2 in.)

» Spring scale

STUDENT ORIENTATION

Orient your students for this STEM project and get them interested by showing a video from this year’s Punkin Chunkin World Cham-pionship by doing a keyword search. Conduct a class discussion focused specifically on the variables that affect the path of the pumpkin shot out of the catapult. Make sure you are focusing your discussion on the projectile design, not on the catapult design. When you orient your students, you will also demonstrate the use of the launch apparatus. But you need to build them first!

BUILDING THE LAUNCH APPARATUSYou will need to build a launch apparatus according to the follow-ing instructions. Make sure that you have about one launch appara-tus for each team. The launch apparatus has three pieces of wood: the base, the launch rail, and the launch angle guide. The equip-ment section in the margin shows the materials needed to build one launcher.

1. Drill a hole for the bolt through the 1x6 approx. 1/2 in. from the side and 5/8–3/4 in. from the bottom. Use a bit the same diameter as the bolt (11/64 bit).

2. Drill the same size hole (11/64 bit) in the dowel (centered) 1/4” from the end so that the launch rail can be moved freely.

3. Draw a center line the length of the base (1x4) on both sides of it. Center the 1x6 on the base and mark where it will be placed next to the center line. Drill two holes through the base (centered) at least an inch from where each side of the 1x6 will connect and drill one of them into the 1x6 so that it can be fastened next to the center line midway along the length of the base. Use a bit slightly smaller in diameter (5/32 bit) than the wood screws.

4. Use a 1/4 bit to enlarge the opening of the hole on the bot-tom of the base so the head of the screw will go in far enough to be flush with the base. Oth-erwise, the launcher will not be flat on the bottom and may wobble on a flat surface.

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5. Before actually fastening the 1x6 to the 1x4, you should determine how you want to put angle measures on the 1x6. There are at least two options for how you can do this.

» Option 1: Make a copy of the half protractor image below and paste it to the 1x6 so the hole of the protractor lines up with the hole on the 1x6 and so the base of the protractor is parallel with the bottom of the 1x6. The one limitation to this is that the center of the launch rail has to be estimated to line it up with the angle measure on the protractor.

» Option 2: Even more precise, after fastening the 1x6 to the base and the launch rail to the 1x6, use a protractor or level app or pro-tractor app on a cell phone to draw a line even with the top side of the launch rail every five degrees on the 1x6.

6. Insert one wood screw up through the bottom of the base into the hole drilled into the bottom of the 1x6 and line up the 1x6 next to the center line before tightening. Once it is tightened, drill another hole into the bottom of the 1x6 through the previously drilled hole in the base. Insert the other wood screw and tighten.

7. Before attaching the launch rail use a hacksaw or other type saw to make a horizontal groove in the end of the launch rail for the rubber band. Insert the bolt through the holes in the launch rail and the 1x6 and fasten with the washer and wingnut.

8. If you did not paste the half protractor to the 1x6, then use a pro-tractor or cell phone app to draw angle lines for every 5 degrees. It helps to have the wingnut fairly tight to get the launch arm in position to draw each line.

9. Mark several lines on the launch rail to serve as pullback points for launches of different forces. To make the increase in force indicat-ed by the pullback lines uniform, use a spring scale to mark equal increases in force. Experiment with the projectiles of three differ-ent weights to find the best pull-to-line and the best large rubber band considering the amount of space you will have to shoot the projectiles. The greater the distance traveled the less minor errors in time aloft measurement will affect the results.

BUILDING THE STOCK PROJECTILESEquipment/Materials

» straw

» cardstock paper

» paper clip

» clay or adhesive putty (sticky tack)

» tape

» large rubber band

» lab balance

Now that you have built the launch apparatus, you need to build some stock projectiles for students to experiment with. Construct approximately three stock projectiles per student group with nose cones of 2 g, 3 g and 4 g. Each group should consist of 3–4 students. One alternative that can save time is to make one projectile and in-terchange three nose cones of different masses.

1. Using a straight edge draw the outline for two pairs of fins on the cardstock. Use the attached diagram as a guide. After using scis-sors to cut them out use the first one as a template to draw the rest of the ones needed for you stock projectiles.

2. Fold the fins so that they will stick out at opposite angles and then use tape to secure them to the straw on opposite sides of the bot-tom of the projectile.

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3. Partially unfold the paper clip and bend it so that a hook is per-pendicular to the straw and bend the other end so that it will wrap around the straw. Then tape it to the straw as tightly as possible so that the top of the hook is even with the top of the straw and in between fins. If forces greater than 7N are going to be used, it is important that the paper clip is securely taped.

4. Use a flat surface to roll the clay or adhesive putty into a cone and embed the end of the straw into the base of the nose cone.

Determine how your students will measure the distances of the pro-jectile flights. If you don’t have an extra-long measuring tape, you can calibrate a string with a meter stick and a permanent marker. The numbers can be written on pieces of tape and attached to the string. Either may be attached to a nail or screw in the board of the launch apparatus. Distances of 30 ft are possible with 7N of force ex-erted by the launcher.

PROCEDURENote: Students should include all notes, designs, data, calculations, analyses, and conclusions in a project log.

Equipment/Materials

» data sheet for each group

» student instructions for each group

» three stock projectiles for each group

» measuring tape (long) or calibrated string

» stopwatch or cell phone

» other measuring tape

» a target of some kind. It probably should be 1–2 ft in diameter

» launch apparatus for each group

1. If you haven’t done so already, divide students into groups of 3 or 4. Each group should determine who will measure the distances, who will shoot the projectiles and measure the launch angles, and who will measure the time aloft.

2. Introduce the activity with a video of the punkin chunkin contest and by demonstrating use of the launcher with one of the stock projectiles. Explain to the students that they will be making their own straw projectiles to launch, but first they will collect some data by launching stock projectiles.

3. Each group will launch three stock projectiles three times each from two different pull back points (total 18 launches). The three projectiles will each have a different amount of mass in the nose cone: 2 g, 3 g and 4 g. Each of these three launches should be at a different angle. The same three angles should be used for each of the three masses. The projectile should be pulled back to the point designated by the teacher plus one other pullback point for each of these launches. Each team should record the launch angle, the distance travelled, and time aloft for each of these launches. The

time aloft could be measured with the stopwatch function of a cell phone if an actual stopwatch is not available.

4. Students should make calculations to determine the horizontal velocity, vertical velocity, and the height of each trajectory.

5. Based on your students testing results determine the location of the target and share this information with your students. Based on their results each member of the team should design a straw projectile to launch at the target. Variations can include the shape of the fins and the mass of the nose cone. The students should also indicate what trajectory angles and pullback points to use to launch their projectiles.

6. After each member presents their design to the team they should discuss the pros and cons of each design and come to a consen-sus regarding which projectile designs to build. They may build as many projectiles as they desire but should come to a consensus as to which two projectiles to launch, what launch angles, and what pullback points to use.

7. Place the target approximately 30 ft. away depending on the amount of space available and what amount of rubber band force you are going to allow. Rubber band forces greater than 7–8 N may put destructive stress on the paper clip attachment to the projectile.

8. After projectiles are built have teams take turns launching their two projectiles at the target. As an accountability measure have team members work with members of another team to make the measurements for their launches. The launcher should give a short countdown for the sake of the student measuring the time aloft.

9. Allow the students the opportunity to revise and retest their designs.

TEXTBOOK CONNECTIONS » Algebra I—Ch. 2–3

» Pre-Algebra—Ch. 2–3

» Physical Science—Ch. 4–5

» Physics—Ch. 3–6

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ASSESSMENT RUBRIC

4–Mastery 3–Competent 2–Emerging 1–Poor

Analysis

The relationship between variables is discussed. Trends or patterns are described and analyzed. Predictions are made regarding possible changes to projectile characteristics.

The relationship between variables is discussed. Trends or patterns are described.

The relationship between vari-ables is discussed. No patterns or trends are mentioned or predic-tions made.

The relationship between vari-ables is not discussed.

Drawings/Diagrams

Designs show understanding of concepts and are easy to understand, and trajectories are included and labeled completely.

Designs show understanding of concepts, and trajectories are in-cluded but are partially labeled.

Designs show understanding of concepts, and trajectories are included but partially labeled.

No designs or trajectories pres-ent, or design is identical to that of another team member with minor tweaks.

CalculationsAll calculations are shown, and the results are accurate and cor-rectly labeled.

Some calculations are shown, and the results are accurate and correctly labeled.

Some calculations are shown, and the results are labeled correctly.

No calculations shown or they are inaccurate.

Conclusion

Evidence is cited to support the conclusion drawn from the activity, and possible reasons are given for errors or success.

Evidence is cited that supports the conclusion drawn from the activity.

What was learned from the experiment was stated.

No conclusions recorded; no evidence of reflection.

Organization/Appearance

Almost all entries are organized, neat, and easy to follow. Num-bers, bullet points, and spaces are almost always used to sepa-rate different items.

Most entries are organized, neat, and easy to follow. Numbers, bullet points, and spaces are usu-ally used to separate different items.

Some entries are organized, neat, and easy to follow. Many are not. Numbers, bullet points, and spaces are sometimes used to separate different items.

Entries are not organized or neat. Order is difficult to follow. Num-bers, bullet points, and spaces are rarely used to separate differ-ent items.

Collaboration with Peers

Always listened carefully to others and offered detailed, con-structive feedback. Participated fully and shared the workload fairly.

Usually listened to others and usually offered constructive feedback. Participated most of the time and usually shared the workload fairly.

Sometimes listened to others, occasionally offered construc-tive feedback. Participated but sometimes did not share the workload fairly.

Did not listen to others and often interrupted them. Did not offer constructive feedback. Did not participate and relied on others to carry the workload most of the time.

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90 100 110 120130

140150

160170

8070

60

50

40

3020

10 170

160

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140

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120110

100 80 7060

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1 to 1.5 in. 1 to 1.5 in.

1 to 2 in.

0.5 to 1 in.

0.25 in.

0.5 to 1 in.

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