Title: Bombs Away! A Ping Pong Catapult

By: Hunter Lash

Experimental Design• Problem- What is the effect of the

length of the catapult on the distance the ping pong ball travels ?

• IV: Length of the catapult arm

• Levels of the IV 30cm (Control),35cm, and 40cm

• DV: Distance the ball travels

Experimental Design

• Constants (3) : same ball, catapult, and testing environment

• Hypothesis: If the length of the catapult arm is 40cm, then distance the ping pong ball travels will be further than the 30cm or 35 cm arms.

• 3 boards of of wood (length 29 cm), 8 boards of wood (length 12 cm), 1 board (length 7cm), and 1 board (length 34 cm)

• Wood screws• 3 large rubber bands• 4 eye hooks• Cardboard• 1 metal bar • 5 ping pong balls• 3 m tape measure

Materials

Procedures

1. Gather materials.2. Build catapult and cradle.3. Set arm length to 30cm. 4. Put ball in cradle and pull it back all the

way.5. Release the arm, measure and record the

distance the ball travels.6. Repeat for a total of 5 trials.7. Repeat steps 3-6 for 35cm and 40cm arm.8. Record and compare all data

Data TableLength

of catapult

arm

(cm)

Trial

1

Trial

2

Trial

3

Trial

4

Trial

5 Averages

30 1.16 1.52 1.46 1.55 1.26 1.39

35 1.56 1.94 1.54 1.55 1.79 1.67

40 1.73 2.02 1.63 1.52 2.14 1.81

Distance (m)

Graph (Trials)

Distance (m)

Graph (Averages)

Length of Arms (cm)Distance (m)

Trial Outliers(Edited and inserted quickly)

• 30 cm Length of Catapult Mean (1.39 cm) – Trial 1 (1.16 cm) – first trail of experiment, didn’t pull

catapult all the way back– Trial 4 (1.55 cm) – gust of wind blew in the window

• 35 cm Length of Catapult Mean (1..67 cm) – Trials 2 & 5 (194 / 179 cm) – catapult length increased as

it was moving forward– Trials 1, 3, and 4 (1.56 / 1.54 / 1.55 cm) – were done

correctly, resulting in more accurate distances

• 40 cm Length of Catapult Mean (1.81 cm) – Trial 4 (1.52 cm) – elastic band broke as catapult was

moving forward– Trial 5 (2.14 cm) – changed elastic band to a slightly

smaller size

Discussion –

• Average Distances for various catapult arms were 40 cm (1.81 m), 35 cm (1.67 m),

and 30 cm (1.39 m).• Analysis: As the length of the arm of

the catapult increased, the distance the ping pong ball traveled also increased (directly proportional)

Conclusion

The hypothesis was accepted

because the longest arm (40 cm) made the ping pong ball travel the furthest.

Conclusion (cont)

• Errors made included: None

• If done differently: – Used a bigger catapult– Tested a heavier ball– Used a different number of rubber bands

Conclusion (cont)

• Overall, this science experiment was a success, because I had a good time building the catapult and doing the experiment.

Questions

• Are there any questions?