Launch Your Inner Engineer with a DIY Catapult

DIY Catapult

Discovery Place Science

There are few things that are as inherently exciting as when things are flying through the air, whether the flying object is a hummingbird, a baseball or Charlotte Hornets’ Miles Bridges going up for a slam dunk.

In this activity, we will use the engineering design process to create our own miniature catapult and send things flying!

Humans love to throw objects fast and far, but there is a limit to what we can do with our arms alone. That’s why ancient and modern engineers created machines that can do it better. One of those early creations was the catapult, a device that stores up energy as potential energy to be released all at once as kinetic energy that throws a projectile much further than a human could alone.

To make our catapults, we will use something that engineers utilize every day: The Engineering Design Process. This is a circular, six-step plan that helps us create the best possible solution to a problem.

Source: NASA.gov

From NASA (who knows a thing or two about engineering), we learn that the engineering design process is:

Step 1: Ask (what problem are you trying to solve?)

Step 2: Imagine (what knowledge do you need to better understand the problem?)

Step 3: Plan (draw or write out a plan including amount of materials needed)

Step 4: Create (build a prototype)

Step 5: Experiment (test your prototype and see how it works)

Step 6: Improve (how can you make the prototype better?)

This isn’t just a guideline for how to solve complex engineering problems; it is a process that can be used for a broad variety of everyday issues. Broken toy? This can help you fix it. Argument with a friend? Try following these steps to figure out a solution – instead of building a machine you are using the steps to plan out the conversation you will have with them.

For today, though, we will be using these six steps to help us build our miniature catapult!

You’ll need around 5 minutes of prep time for this activity and can expect the learning time to be anywhere from 10-60 minutes or more.

This activity is well suited for children in grades three through five.

Materials List:

While this is the list of materials we used for our catapult, your materials may vary.

  • Rubber bands (the more the merrier!)
  • Hot glue guns and glue sticks
  • Scissors
  • Popsicle/craft sticks
  • Straws
  • Paper clips
  • Clothespins
  • Mini marshmallows
  • Chopsticks
  • Pipe cleaners
  • Cups
  • Markers
  • Bottle caps,
  • Pencils
  • Paper
  • Bowls
  • Tapes (scotch, masking, and/or duct)

Directions:

Remember, we are going to use the engineering design process we mentioned above as a guide for making our catapult. So, let’s look at the six steps:

  • ASK: Our task is to make a catapult using the materials we have on hand, but how will we do this? 
  • IMAGINE: What do catapults look like? How have people made them with household materials?
  • PLAN: Choose just a couple of your best ideas to sketch out in more detail and decide on which one you want to make.
  • CREATE: Build your catapult based on your plan.
  • TEST: Test your design to see how well it works. How far and how accurately can your catapult fire the projectile? What parts are working well, and what could use tinkering?
  • IMPROVE: Based on your test results, what about your design could be improved and why? What might you change to make it better? Let’s build a second version!

Once you’ve gone through all six steps, the process begins again at the beginning. Keep going through the cycle until you are satisfied with your design.

There are numerous ways to make a catapult using materials found at home and we encourage you to try different ways. To get you started, here is one possible method, followed by photos of other example builds. Materials can (and should!) be substituted as necessary. Experiment with different variations or create a unique design.

Simple craft stick catapult:

  • Stack five craft sticks together and wrap a rubber band around each end
  • Stack two craft sticks and wrap a rubber band around only one end
  • Slide the five sticks in-between the two sticks, as shown
  • Wrap a rubber band where the two sections meet to hold the catapult together
  • Attach a bottle cap to the top stick to hold the projectile
  • Place a projectile (mini-marshmallow, small ball of paper, etc.) in the cap, hold the stick down, and release!

Here are some other designs to consider as you make your own:

How to adjust for younger and older learners

For younger learners, create targets using paper, bowls and pencils/markers to make a launching range or game.

For older learners, practice measurement and division by calculating your projectile’s overall speed. To do this, measure how far it traveled in inches (or another unit of measurement) and the time from launch until landing. Then divide the distance traveled by the time to find the projectile’s velocity. Find the average velocity by adding the velocities of your trials all together and dividing this figure by the number of trials. Compare different catapults to see which launches the fastest projectiles Use a table like the one below table to record your data.

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