Shout out to Jessica's Dad for helping us with the construction and letting us use his tools and supplies.

Final Product

Physics Behind the Catapult

Force

A trebuchet is powered by gravity or a force strong enough to launch an object. The force is on the end with the counterweights, and the projectile on the other. Gravity brings down the counterweights, allowing the arm and sling to fling over. The weights enact a force on the catapult, allowing the projectile to launch. A centrifugal force acts upon the sling, allowing it to keep it hooked onto the catapult as it flies out when launched. The trebuchet  also demonstrates Newton's Third Law of Motion: when an object exerts a force on another object, the second object exerts an equal and opposite force on the first one. 
Energy

A trebuchet deals with both potential and kinetic energy. While the counterweight is in the air it has potential energy. Once the trigger is released, allowing the counterweight to drop, the potential energy transfers to kinetic energy. Being brought down by gravity the counterweight causes the arm to swing, dropping the counterweight and flinging the water balloon in the sling upwards.

Projectile Motion
Catapults demonstrate not linear motion, but non-linear motion which is presented as our projectile, the water balloon, takes a curved path of motion when launched. Because the water balloon takes a curved path, it can be labeled as a projectile. Therefore projectile motion or parabolic motion has both vertical and horizontal components. The horizontal component (x) can be found by using vix= viCos θ. The vertical component (y) can be found by using viy= viSin θ.
            The catapult consists of both vector and scalar quantities.  Scalar quantities have magnitude alone. Scalars in projectile motion include time. Vectors have magnitude and direction.  Vectors in projectile motion include displacement, velocity, and acceleration.

Painting the Catapult

We met up on Sunday, May 19th to paint the catapult.

Members present:

Jessica

Mckenna

Yadi

Trial Four

Launch distance: 34 ft.

In this trial, Yadi rearranged the way the sling was put on. She made sure the face mask was facing upwards,  which allowed to her to pull the projectile into a more straight position for launching.

Trial Three

Launch distance: 32 ft.

In this trial, we added on a two pound weight that was sitting in the garage. The increased counterweight on the trebuchet allowed the projectile to launch further.

Trial Two

Launch distance: 23 ft.

The changes we made were in the sling.

Instead of using the net mesh we originally had, we switched to a face mask.

At one point we were considering using a bra for the sling.

Trial One

Launch distance: 0 ft.

Our first trial was unsuccessful with our sling being unable to release the water balloon. 

Trigger and Sling

This is the trigger for the catapult.

  A string is tied onto the trigger, and when the string is pulled the trigger is released from the eye hook allowing the weights to go down and launch the projectile.

Mckenna pointing to the trigger

A 24 in. of string is tied onto the bottom eye hook, and the string is then connected to the sling. Then a 28 in. of string is tied onto the other side of the sling, with a eye hook tied to the end of it. The eye hook is then hooked onto the nail at the top of the throwing arm,  which comes off once the projectile is released.

Our first sling

The Bar, Throwing Arm, and Counterweights

My father had a metal rod which came from some car part. He cut it up and we made large holes on the side for it to go through.

Jessica drilling the holes into the side of the catapult for the bar.

Jessica inserting the bar into the catapult.

After the holes for the bar were made, we created a throwing arm. The throwing arm measures to be 40 inches long.

Yadi added on the counterweights, which were twenty pounds total. The counterweights were spare weights we found in Jessica's garage.

Building the Base

We first began construction with Yadi and Mckenna measuring the pieces of wood we were going to use.

The base of the catapult is 3x1 ft., with the sides being 2 ft. tall. 13 inches into the base, we added diagonal side braces which were 28 inches long. 

My father is really into construction, so we had a lot of spare wood to use for the catapult.

Jessica cutting the wood for the base.

This is how the base of the catapult turned out.

We then screwed on a flatboard to the surface so the projectile will have a smooth surface to launch off of. 

We met up to construct our catapult on Friday, May 17th.

Members Present:

Jessica

Mckenna

Yadi

Materials Used

Catapult Structure

Two 3 ft. long pieces of wood for the base

Two 1 ft. long pieces of wood for the base.

Two 2 ft. long pieces of wood for the sides.

Two 28 in. long pieces of wood for the side braces.

1 1/2 ft. long flat board

Metal Rod for the bar

One 40 in. long piece of wood for the throwing arm

Counterweights

Two twenty pound weights

One two pound weight

Small metal rod to place the weights on

Zip ties to hold weights together

Trigger and Sling

Four eye hooks

One regular hook

One Nail

Net mesh (first sling)

Face mask (second sling)

One 24 in. piece of string

One 28 in. piece of string

One 5 ft. long piece of string

On May 11, 2013 all the members gathered together to discuss the project.

No construction began, but we planned out what days we would meet, a plan for the catapult structure, and which materials we were going to use.

Our catapult plan derived from this video http://www.youtube.com/watch?v=rXSpmxrCEn4

Members Present:

Jessica

Mckenna

Yadi