Curious Catapults

The catapult project is a creative and different way of displaying our knowledge of quadratic equations. Each team was to build a catapult that is capable of holding and shooting a table tennis ball in an arc. After the process of building, the shot of the catapult was filmed and put into Logger Pro, which gave a quadratic equation that roughly matches the arc of the table tennis ball. The purpose of this project is to solidify our understanding of quadratics and to know how quadratic equations can be applied to real-world situations.

My team (Angela and I) decided to use this catapult’s design. It is simple to build, while not requiring any wood cutting or complex structures.

One problem we had with this design was that the ball would not shoot upwards in an arc, but would shoot sideways. This caused the ball to be too low. To deal with this problem, a pencil was placed above the component that holds the ball when it is pulled back. With the pencil, the part of the catapult that launches the ball would stop before moving its maximum distance, making the ball fly at a higher angle.

I believe the hardest part of this project was evaluating whether the catapult’s design would be strong enough or if it needed modifications. Building and testing the catapult is not hard, but the planning and the modifying process may take a long time and/or be difficult because it involves a lot of trial and error.

My understanding of quadratic equations improved as I learned how quadratics are used in a real situation and how they can be used with different axes to represent different types of data (for example, height vs. time and height vs. distance are different and used in different contexts).

I believe the design process is important when doing a project like this, but the mathematical understanding of the catapults is the most important, especially in a math class. The unit of quadratics is possibly the most important of Algebra I, and there is no better way of showing understanding than in a real-life situation.

Catapult Video (download)


Polymer Journal 4 – Reflection

Prototype #1:

By mixing Super Slime and Boogers together, we made our first prototype called “Super Booger”. It was very stretchy and gel-like without being too sticky or wet. It seemed perfect for our design goal. One thing I would change was that even though it seemed simple to make with just two base polymers, it took a lot of extra materials to perfect and adjust it to how we wanted. This polymer was unique but hard to create.

Prototype #2:

Our second prototype called “Super Everything” attempted to combine Gloop, Boogers, Super Slime and Oobleck together. The result was stretchy and gel-like just like our first prototype, but it was sticky and was very wet as we had added a large amount of water for the Oobleck. In the end, it was too sticky and hard to clean to be a polymer that was meant to keep things together without damaging them.



We performed a few tests on Prototype #1 to see if it was really that strong. It was poked slowly and quickly to see if any of it would stick to a surface. The polymer only left the object wet for a few seconds and none of it was displaced. It was stretched extremely long and held in the air at the sides to see how long it could go without breaking. It stretched for over ten meters and did not collapse to pressure. It was dropped at around a one-meter height and bounced instead of splattering across the table.

Our first prototype is the most effective at performing its intended purpose. Since our goal was to create a polymer that holds things together like a piece of string or an elastic band, Prototype #1 proved to be much stronger. Both prototypes were fairly stretchy and gel-like, although the first prototype was much less slime-like and held its form better. Its non-sticky and dry properties made it superior to its alternative, due to the polymer’s ease of use and cleanliness.

If we had more time allocated for us to work on this product, I would try to find a way to make it less wet, as even though it left no stains or damage, it visibly left a mark when placed on the table.

I believe we did fairly well in these steps of the design process; however, two prototypes may not be enough. If we had more time to create more than two different types of polymers, we would have had a more complete and finalized product. Our prototypes should have also been tested and observed more, to see the strengths and weaknesses of each design.

Here are the steps to create our polymer, “Untangled Slime”:

  1. Measure 55g of glue in a cup.
  2. Measure 40mL of PVA solution in a graduated cylinder and pour into a separate cup.
  3. Measure 40mL of laundry starch in a graduated cylinder.
  4. Measure 8mL of borax solution in another graduated cylinder.
  5. Pour the borax into the cup with the PVA solution and stir for a few minutes while mixing the laundry starch with the glue, stirring both simultaneously.
  6. Combine the two polymers together in a large beaker, adding around 5mL of borax to the mixture if necessary to help the two polymers mix.
  7. Pick up the mixture and mold it until the two polymers have visually combined into one.