Building a Catapult
Punkin Chunkin for Science
Trying to mix some fun into physics, and it being October, I decided to help the kids learn about catapults using mini, candy pumpkins. We tried our hand at building a catapult… for science of course!
The design is fairly easy and you don’t need many materials. My kids, especially my boys, had a blast making them and it did help them remember more about catapults. I have found that hands-on activities can sometimes help people retain more information and keep them engaged. This activity was no different!
About Catapults
Catapults are simple machines that use stored potential energy to carry out a task. They are considered a ballistic device, which means it is something designed to launch something with a decent amount of force.
Catapults have been used for centuries and in ancient times, they were the biggest line of defense against enemies. One of the earliest dates back to the 7th century BCE, and while a slingshot doesn’t look like the traditional idea of a catapult, it is a catapult.
Learning how to use a slingshot can be useful but I wanted the kids to build something, so I opted out of that and focused on a more “traditional” catapult, and being it was around Halloween, I thought the pumpkin candies would be great to use. I will admit that I did consider for a second roping my hubby into making a bigger catapult to chuck actual pumpkins, but I am glad we didn’t dive that deep!
Let’s Build
Building your catapult doesn’t require much but as I used bottle caps as the bucket, there might be some preplanning if you don’t use plastic bottles. We normally don’t, but when we do pizza night or something like that, we will grab some drinks, and I will confess… I save the caps. I’m not hoarding mountains of caps, I have half a dozen or so on hand sometimes, but usually they come in handy for something!
What You Will Need
- jumbo popsicle sticks
- rubber bands
- glue gun and sticks, regular glue, or glue dots
- bottle cap
- candy pumpkins
Building the Catapult
- Gather your supplies. I used a hot glue gun because my kids were old enough to handle it, however, regular glue could be used. The cap would need longer to dry, but I would think it would work.
- Make 2 stacks of popsicle sticks. One with 2 sticks and a rubber band around one side, and the other with 5 sticks and a rubber band around both sides.
- Slide the thicker stack into the stack with only 2 sticks. Prepare 2 rubber bands.
- Use the rubber bands in a criss-cross method to keep the stacks secure.
- Attach the cap to the top of the stick. If using regular glue, you might want to do this step before the last one.
- Place your pumpkin, or other small object, into the “bucket” and have fun!
Here are our catapults. You will notice that one is a bit different and that is because my oldest played a bit with the logistics of the design. I would say to encourage that because it can help with the understanding of how it all works!
Notes:
- To allow kiddos to personalize their catapults, you could allow them to paint or color them before hand
- To bring color without the paint, buy colored sticks and/or rubber bands
- If you don’t want to use glue, rubberband a plastic spoon to the top of the catapult, with the spoon being the bucket.
- To have more fun, set up targets
- If you don’t want to use pumpkins, use other items, like ping pong balls, marbles, pompoms, or what ever you have on hand.
How Does a Catapult Work?
Catapults are devices that take potential energy and make something move. There are 3 general ways to store the energy, torsion, tension, and counterweight (gravity). Once a catapult has potential energy, that energy can be released, allowing the stored energy to become kinetic energy. The arm of a catapult and angle of the release affect the range of arc on what is being propelled. Gravity and the forward momentum allow the item to reach a specific mark.
So, the potential energy of the popsicle catapults are our fingers pushing down on them. The potential energy becomes kinetic energy when we trigger it by releasing our finger. The size of the stack of popsicle sticks and the height of the arm decide on the arc of the pumpkin. The kinetic energy pushes the pumpkin forward, with gravity helping guide it back down.
This is also a great time to discuss Newton’s Three Laws of Motion.
- Law 1 – An object at rest stays at rest, and an object in motion stays in motion with the same speed and direction unless acted upon by an external force.
- The catapult does nothing unless force is applied
- Law 2 – The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass
- The amount of force put on the catapult will change the force of the object
- Law 3 – For every action, there is an equal and opposite reaction
- When the catapult arm is released, it pushes the pumpkin forward with a force equal to the force it exerts on the arm in the opposite direction
Things to Discuss During and After the Project
- How does the force applied to the catapult change the trajectory or distance?
- How does the number of sticks on the middle stack change the distance or range?
- Is the catapult accurate? Why or why not? How could you make it accurate?
- Does the weight of the object being propelled matter?
Having Fun with Physics
This was an easy and fun project, that actually can be played with after building. Below is a video of my boys trying it out for me, and while this coincided with fall for us, you could do this anytime of year. You could chuck Easter eggs across the room, chocolate gold coins, marshmallows… or try various items to discuss how the weight and mass of an object affect everything!
If you are wanting to dive deeper into physics, there are many tools for that. Head to my Amazon Store for a list of Physics Tools for kids!
If you build a catapult, I would love to hear about it! Comment below or head over to Instagram or Facebook, share your pics, and tag me @bemandfam… I’d love to see them!
Don’t forget to pin this for later and if you like Pinterest, I am there too!
Happy Building!
BEM and Fam 🙂 
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