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These catapults look like an automatic slingshot. A trebuchet uses energy from the falling object (its weight)  to power its arm (the sling), which in turn shoots its object. This method is a plus because it can launch projectiles at high speeds, heavier  and farther. But it also has its downsides, it’s not very flexible-all its parts are stuck where they are and only the arm moves. You also have to calculate your weight each time to counteract your projectile. Lastly, the trebuchet remains stationary during a launch; you cannot move them (in comparison to the others).

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This type of catapult looks like a crossbow. It fires by releasing some form of stored tension, whether that is a wound string or a flexed piece of wood. Typically, a rope connects two pieces of wood, on the part that looks like a bow. This string is pulled back and locked in place, ready to fire its projectile. Potential energy is stored in the string, which in turn becomes kinetic energy. Because of the firing mechanism, the projectile launched has to be light, which can’t do much damage which is a big downside. The plus is the projectiles can heavily impact one spot precisely.

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This catapult has an arm that resembles a spoon. The arm can hit the frame of the catapult; this would launch it at 90 degrees or a bar can be added, stopping the arm at the desired angle. However, these catapults aren’t very energy efficient because of how much stored energy the arm takes up during the launch.  The only way to decrease the amount of energy the arm takes up (so the energy can go elsewhere) is to make sure the bucket and payload is light and the arm is durable.

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Alba, Stephanie. “Ballista, Mangonel, &amp; Trebuchet.” Prezi.com, 20 Dec. 2013, prezi.com/fx3wuvl7fatv/ballista-mangonel-trebuchet/.

“Ballista - Physics of Catapults.” Google Sites, sites.google.com/site/physicsofcatapults/home/how-a-catapult-works-the-physics/ballista.

“Catapult Physics.” Real World Physics Problems, www.real-world-physics-problems.com/catapult-physics.html.

“Catapults You Can Make.” Timeline and Development of the Catapult, www.stormthecastle.com/catapult/development-timeline-of-the-catapult.htm.

Contributors, HowStuffWorks.com. “How Does a Catapult Work?” HowStuffWorks Science, HowStuffWorks, 8 Mar. 2018, science.howstuffworks.com/transport/engines-equipment/question127.htm.

Doe. “Diagram Of Ballista.” Auto Electrical Wiring Diagram •, 30 Oct. 2018, 6weeks.co.uk/diagram-of-ballista.html.

Hathaway, Jay. “Trebuchet Memes Are a Thing-Meet the Season's Hottest Medieval Siege Engine.” The Daily Dot, 21 Nov. 2016, www.dailydot.com/unclick/trebuchet-memes/.

“Trebuchet Physics.” Real World Physics Problems, www.real-world-physics-problems.com/trebuchet-physics.html.

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Once our catapult is in its locked position, a clothespin raised by a straw is in control of the arm. As the clothespin is opened, the arm is released and the kinetic energy is put into the rubber bands, moving the arm towards the frame. The arm hits the frame launching our cotton ball out from our cup.

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Three things we could've done to make our catapult better:

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Three things we could've done to make our catapult better:

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1. We could have secured our release mechanism better. As we went through our shots on presentation day, our release mechanism became slightly detached from our platform. This made the arm releasing somewhat unpredictable.
2. We could've changed many aspects in order to get the cotton ball closer to/in the cup. One of these would have been calculating the angle needed to send our cotton ball soaring high enough to fall into the cup, if we found this angle we could've moved our stopping bar leaving our cotton ball closer.
3. We could have taken more practice shots in order to know consistently how far it would shoot and how to take that in consideration with the wet-ness of our cotton ball.

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- cardboard (base)
- popsicle sticks (20)
- rubber bands (4)
- clothes pin (1)
- straw (1)
- cup
- tape
- glue
- cotton ball

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Length: 30cm
Width: 24cm
Height: 18 1/2cm

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Air time:
Time 1 - 0.74s
Time 2 - 0.82s
Time 3 - 0.75s
Average - 0.77s

Landing Distance:
Distance 1 - 3.47m
Distance 2 - 3.52m
Distance 3 - 3.08m
Average - 3.36m

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Horizontal component: 4.36m/s
Maximum altitude: 0.75m
Time to reach max. altitude: 0.39s
Initial vertical velocity: 3.83m/s
Initial resultant velocity: 5.8m/s