Physics Catapult

Mia Maher 11-9-15 H. Conceptual Physics period 7 The Catapult Introduction: Catapults were often used in the Middle Ages as weapons in castles. However, they were originally developed in China, around 3 and 4 B.C., long before the Middle Ages. At this time, they were more like a crossbow. They evolved, however, being made mounted onto stands. The catapult I made had to shoot a marshmallow five meters. My design was called a “torsion catapult.” I chose this design because I wanted to build a catapult that closely resembled one that was built in the middle ages. Instead of springs or rubber bands, they used string to power their catapults. This catapult connects to physics for many reasons. After testing the catapults, recording their times and distances, we are able to use that information to find our initial velocity of the marshmallow. We do this by using the kinematic equations, used in physics to find different variables of projectiles in motion.

Design Plan: Materials                

2 - ¾” x ¾” x 12” blocks of wood 1 - ¾” x ¾” x 10” block of wood 5 - ¾” x ¾” x 5” block of wood 2 – 5 ½” x 3 ½” x 6 ½” triangular wood pieces 3 – ¼” (diameter) dowel rods 1 – 8” metal rod 1 – plastic cup 3 – small eye screws 18’ of twine 8 – 1 1/8” screws 1 - ¾” screw and washer 10 – ¾” tacks Glue Drill ¼” drill bit 9/32” drill bit Saw Diagram- (attached)

Data Analysis:

Mia Maher 11-9-15 H. Conceptual Physics period 7 The Catapult

Data table-

Distance

Time

Vx0

Vy0

V0

4.91 m

.64 s

7.67 m/s

3.136 m/s

8.29 m/s

5.38 m

.65 s

8.28 m/s

3.185 m/s

8.87 m/s

5.21 m

.75 s

6.95 m/s

3.675 m/s

7.86 m/s

Average Vx0: 7.63 m/s Average Vy0: 3.392 m/s The initial velocity (y) was determined by using the kinematic equation Vy = Vy0 + Ayt, where Vy was final velocity (0), Vy0 was initial velocity (what I was solving for), Ay was acceleration (9.8, gravity), and t was time (1/2 of each time recorded above). The initial velocity (x) was determined by using the formula Vx0 = d/t, where Vx0 is initial velocity (what I was solving for), d is the distance (each distance recorded above), and t is the time (each time recorded above).

Conclusion: My catapult was able to launch my marshmallow 5 meters, just as intended. A possible error in my project could be that my releasing mechanism did not work as intended. I had to hold it down and release it manually. In doing this project, I learned more about the kinematic equations and how to use them in a demonstrated situation. I also learned a lot more about the history of catapults. A lifelike example of a projectile whose landing spot must be carefully predicted is a fishing pole/fisherman, when the fisherman throws his bait in the fishing pole out into the water. Another example would be military aircraft carriers launching aircrafts into the air when there is only a short runway.

http://www.ehow.com/info_8597229_modern-uses-catapult.html http://www.stormthecastle.com/catapult/the-history-of-the-catapult.htm