🎯 Catapult arm length: the whole packet

🎯 Catapult arm length · 3rd–8th grade · 1 day of testing · free · 50 minutes a sitting

My days, if the fair is 14 days away

Count back from your fair day and write in each date. Fewer days than this? The jobs share days, in this order; nothing is skipped.

Dates from my teacher

• My question is due
• Testing starts
• My results table and graph are due
• My board is due

In this packet

1. 🗓️ My project plan
2. 💭 My hypothesis
3. 🧺 Change, measure, keep the same
4. 🪜 My steps
5. 📊 My results
6. 📓 My logbook
7. ✅ My conclusion
8. ✂️ Board titles to cut out
9. 🏅 The judge's questions and my certificate

If I change how long the catapult's throwing arm is, then how far the paper ball flies will ________________, because _____________________________________________

What I think will happen, in my own words:

3 levels × 3 tries at each = 9 tries in all. If anything you keep the same changes, you won't know which change made the difference.

What I need

• 🪵 Craft sticks: 8
• ➰ Rubber bands: 4
• 🧢 A bottle cap
• 📄 Paper: a scrap, scrunched into one ball
• 🩹 Masking tape, to mark lines
• 📏 A tape measure, or a long ruler
• 🩹 Tape
• 📏 A ruler

Be safe: 👶 Small parts · 🙅 Never at faces

1. Build the craft-stick catapult from the Workshop, but leave the cap off for now.
2. Tape the cap to the very end of the top stick: that's the normal arm.
3. Stand the catapult on the floor with its back edge on a masking tape line.
4. Put the paper ball in the cap, press the arm all the way down, and let go.
5. Aim across the room, never at anyone, and measure to where the ball first lands.
6. Write it down, then launch two more times.
7. Tape a second stick along the arm so it sticks out 3 cm farther, and move the cap to its end.
8. Launch three times, then slide the second stick out to 6 cm and launch three more.
9. Find the mean for each arm and draw a line graph.

Write each number in your results table the moment you measure it.

I changed: Arm made longer by   I measured: how far the paper ball flies (cm)

MY GRAPH (a line graph: arm made longer by along the bottom, cm up the side)

What I noticed: ______________________________________________

Write something every day you work on it, even the days you only gather things. More days? The three-page logbook prints from peabody.kids/science-fair/templates/logbook.

My hypothesis was ☐ right ☐ partly right ☐ not right.

I know because my numbers show:

What surprised me, or what might have gone wrong (7th and up):

Next time I would test:

Idea: Change a second thing: launch the paper ball and a heavier ball of foil from each arm, and draw a line for each.

1. What made you want to ask this question? Say something like: I wanted to know: does a longer arm make a catapult throw farther?
2. What did you think would happen, and why? Say something like: I thought changing how long the catapult's throwing arm is would change how far the paper ball flies, and I wrote down why.
3. What did you change, and what did you measure? Say something like: I changed how long the catapult's throwing arm is (0 cm, 3 cm, 6 cm) and measured how far the paper ball flies in cm.
4. What did you keep the same, and why does that matter? Say something like: I kept the same paper ball and pressing the arm all the way down every time the same, so only how long the catapult's throwing arm is was different.
5. How many times did you test it? Say something like: 3 times at each of my 3 levels, and I found the middle number.
6. What did you find out? Show me in your numbers. Say something like: Look at my table: 0 cm and 6 cm gave different numbers, and here's the pattern.
7. Was your hypothesis right? How do you know? Say something like: My numbers show whether I was right, partly right or not, and I can show you where.
8. Did anything go wrong, or surprise you? Say something like: One try was odd, so I did it again and wrote it in my logbook.
9. If you did it again, what would you change or test next? Say something like: I'd change a second thing: launch the paper ball and a heavier ball of foil from each arm, and draw a line for each.