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.

Physics Traffic Light Lab: Burnet & Romeria

Introduction

Upon receiving this assignment, Supertramp assembled within seconds of the secret call and decided on a location to collect data (Burnet Ln. and Romeria Rd.) a "T" intersection located near Lamar Middle School. We chose this particular intersection because of the light's rediculous length and complete inconvenience.

The purpose of the lab is to determine the amount of time necessary to traverse the intersection, in order to estimate the safety of clearing the intersection at a reasonable speed once the yellow light commences.

Procedure

Initially, we determined the length of the yellow light by recording the light's duration on video. This allows us to record the length of time of the yellow light.

Then, we determined an approxiamate length of the intersection (using Google Earth) approxiamated because the intersection involves a left/right turn.

Thus, by recording the length and reasonable speed for traveling, we determined a reasonable deceleration while taking the turn, and the amount of time necessary to execute such a turn.

Mathematical Equations


x= vt


22m (Curve Length) = 8.9 m/s (Safe Speed 20 m.p.h.) x t (Seconds)
t = 2.47s

Acceleration x Time + Initial Velocity = Final Velocity

a(1.53) + 13.4 = 8.9

Acceleration = -2.94 (reasonable)

4-2.47 = 1.53    

13.4 m/s = 30 m.p.h. (Speeding when light turns yellow)

X + 3.5 (Average Length of Car) = (1/2) (-2.94 m/s/s) (1.53)^2 + 13.4 (1.53)
-3.44 + 20.5 = 13.56

A 0.53 + 13.4 = 8.9

A= -8.9

Acceleration at -8.9 m/s/s is ridiculous, therefore we suggest the addition of at least 1 second to the yellow light.


Conclusion

The duration of the yellow light is unreasonable, and in order for a person to make the turn successfully they would have to decelerate a ridiculous amount, we will suggest to the city of Austin to extend the length of the yellow light, in order to encourage safety in our city.

http://maps.google.com/maps?hl=en&tab=wl

Galileo's Lab

Faron Stout

September 9 2011

Galileo’s Lab

By means of a metal ramp and timer, my group (consisting of Carl Romines, Audrey Mannix, Dillon Johns and myself) attempted to recreate Galileo’s experiment of proving that distance traveled under the influence of gravity is equal to the square of the time.

Everyone is aware of the experiment involving the leaning tower of Pisa to demonstrate the properties of gravity, but Galileo also utilized the ramp experiment to prove the hypothesis:

Distance fallen is equal to the square of the time or duration of fall

which happened to be identical to my group’s hypothesis, more or less eloquently put.

Galileo was accredited with the verification of this hypothesis, despite the fact that it was discovered by Nicole Oresme during the 14th century.

Equipment:

• Ramp
• Steel Ball
• Stop Watch
• Meter Stick
• Sense of Humor

Accurate Diagram:
(Dillon Johns not pictured)

Data:

http://amannix.blogspot.com/
Conclusion:
So, it turns out that Galileo was right. Who would have guessed? No one in my AP Physics class I’m sure. So, if Mr. Wright’s intention was to make sure I was never to forget the formula              ( d ∝ t 2 ), he may have just succeeded.

Bib’
http://en.wikipedia.org/wiki/Galileo_Galilei