Catapult Lab Write-Up

Introduction

Presented with the assignment of launching a tennis ball via catapult one meter away from a target which was blocked by a one meter high wall, Carl Romines, Dillon Johns, and myself (team name: Supertramp) began immediately on brainstorming ideas and fleshing out prototypes. I could tell Mr.Wright was excited with Supertramp's prospects of success when his eyes twinkled upon viewing our sketch for the catapult design. I don't remember his exact words, but recall the words "genius" and "unbelievable."

So Supertramp  began construction.

Some Background Information

The  word "Catapult" originates from Greek "Kata" (Downward) and "Pultos" (Small round battle shield).

First recorded use in 399 B.C.E. against the Moyta in Sicily (Predating the Crossbow).

Revived in the Midieval era, used to breach castle walls and moats.

Revived again in WWI through the use of trench warfare (to fling grenades and smoke bombs)

Different Types of Midieval Catapults:

• Ballista
• Springald
• mangonel
• Onager
• Trebuchet
• Couillard

Some Calculations

Air Times (seconds)
.47
.52
.40
.48
Average Horizontal Displacement: 2.6 meters
Height of Catapult: 43 centimeters

V(sub y max)= 0
Vy= rsin 0                       Vymax=Vy + at
Vx= rcos0                       0=1.39 + (-9.8)t x t
                                        t= 0.14 at Y max

Vx = 0.43= (-1/2 (9.81)t x t) /t
r= 2.6/t/cos0
Vy= 1.39
r= 1.39/sin(29.27)
r= 3.10 m/s

t= (0.47+0.52+.040+.048+.047+.041)/6
t=0.458s

2.6/cos0 = (0.43+1/2(9.8)t x t )/ sin 0
tan 0 = (0.43+4.9t x t)/2.6
tan 0 = (0.43+4.9 (0.458 x 0.458)/2.6
tan 0 = 0.56
0= 29.27

Ymax= -1/2(9.8)(0.14x 0.14) + 1.39 (.14)+0.43= 0.714m

The Design
Materials:

• PBC piping
• Bungee Cords
• Wood Base & Arm
• Metal Hardware
• Clamps
• Tennis Ball

Relating to Projectile Motion

As a group, we understand projectile motion much more than prior to the project, because we were able to get a clear idea of the adjustments you can make (launch angle, initial velocity) and how that influences displacement, etc. Also, it was a great opportunity for Supertramp to bond as a group.

Next Time

As a group we agreed that next time it would be more effective to build a device that could be launched not using manual force but some sort of device to hold the potential energy until released. Additionally, the catapult was very uncomfortable to launch due to the large amount of necessary applied force, and the damage that it could do to the thumb of our hands.