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Gourd Group Pumpkin Launch

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Katherine Logan

on 28 January 2014

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Transcript of Gourd Group Pumpkin Launch

The Gourd Group
Period H
A. Izzo, C. Siegman, E. Tein, E. Discepola, K. Logan

The objective of building our own catapult to launch a pumpkin was to connect the physics of circular motion, forces, and projectile motion and combine it into a hands-on project. Being mindful that we were working with powerful tools, we designed and constructed our catapult. Then we test launched a couple of smaller pumpkins approximately 2-3 kg each. We measured the distance they traveled from the point of release and worked backwards to find the force on the pumpkin. We were a tad bit disappointed with the distance our pumpkin traveled; however, we learned a lot about building a catapult and how catapults work.
Our Procedure:
Design a catapult utilizing our knowledge of centripetal force and projectile motion.
Construct catapult (with adult supervision).
Test catapult.
Use data collected from trials to determine the values of forces and motion in our catapult.
Make any adjustments necessary to achieve maximum distance and mass at actual Pumpkin Launch.
(Detailed out in the following presentation)
Table #1-Altering Pumpkin Mass

Katherine and Emily

Emily and Alice
and Ellie
*Coloring by Alice*
Trial 1-
Distance vs. Time
acceleration vs. time
velocity vs. time
Trial 2-
distance vs. time
velocity vs. time
acceleration vs. time
"Conifer Catapult." Mythbusters. N.d. YouTube.
YouTube, 07 Apr. 2010. Web. 20 Oct. 2013.
Cuomo, Serafina "The Sinews of War: Ancient Catapults. Science. Science Magazine, 6 September 2004. Web. 30 October 2013.
How to Build an Awesome Catapult. 20 Janurary 2013.
Youtube. Web. 16 October 2013.
Smart Car Sized Torsion Catapult. 13 March 2011.
Youtube. Web. 16 October 2013.

Assorted Research

In this experiment, we were able to achieve our goal of designing and building a fully operational catapult. In our trials, the average force with which it launched was 14 N, and the pumpkins had an average impact velocity of 5.7 m/s. The catapult arm’s acceleration was circular, so we had to use our knowledge of circular motion to find the distance over which the acceleration took place. This was used to calculate the acceleration rate, which was then used in tandem with our knowledge of projectile motion to calculate the final vertical velocity and total impact velocity. As a result of these calculations, we proved our hypothesis that a catapult worked as a result of both circular and projectile motion.
We encountered much trial and error during this process. We intended to have springs as part of the trigger mechanism of the catapult, but were unable to incorporate them. We intended to have higher legs, with more support beams joining them together, but we realized that this would make the catapult too high, because we planned to tilt it so it would launch at a more optimal angle. In the final design we launched the pumpkin out of a basket. We had originally planned to have it launch from a sling that would release and fly off. We had the sling assembled and attached, but once we tried to launch with it, the basketball kept catching on the front of it and therefore did not go anywhere. We had to change our design several times, but eventually were able to address all the issues.
In the related scientific article, which discussed the use of catapults in ancient times, we found many similarities to our own catapult. The Mesopotamians designed them through trial and error, so the designed continued to improve over time. However, their catapults were far more effective than ours, launching 27 kg projectiles 150m. As catapults were the primary weapons for much of ancient times, those who could build them were in demand. Engineers rose in status as a result of the popularity of the catapult, showcasing the importance of understanding the physics behind such a weapon.

Trial 1
Trial 2
Full transcript