Building a catapult is an exciting project that combines creativity, engineering, and an understanding of basic physics principles. In this guide, we'll take you through the step-by-step process of constructing two different catapult designs using simple materials like popsicle sticks, rubber bands, and a plastic spoon. The first design is more simple to make and may be ideal if you're getting hands-on help from younger ones. We had fun with this design, but preferred launching from the second catapult. The second was easier to control the aim and we had more fun with targeting games.
Understanding the Engineering and Physics
To gain a better understanding of how your catapult launches items with very little energy input, here's a deeper dive into the engineering and physics principles involved:
Mechanical Advantage
The design of your catapult utilizes the concept of mechanical advantage. The tension in the rubber bands stores potential energy, which is then released upon launching. This stored energy allows the catapult to exert a greater force than what you apply directly to the spoon.
Elastic Potential Energy
As you stretch the rubber bands, they store potential energy. This energy is transformed into kinetic energy when the rubber bands snap back to their original shape, launching the object. The conversion from potential to kinetic energy is a result of the elastic properties of the rubber bands.
Lever Action
The X-shaped framework and the horizontal stick at the bottom create a lever system. When you press down on the spoon, it pivots around the horizontal stick, producing a lever action. This lever amplifies the force you apply, allowing the catapult to launch the object farther.
Projectile Motion
When you release the spoon, the potential energy stored in the stretched rubber bands converts into kinetic energy, propelling the object forward and upward. The launched object follows a curved trajectory, known as projectile motion. Gravity influences the object's path, causing it to travel in a parabolic arc until it reaches the ground.
Continue below for guides on how to make the two catapult designs!
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Catapult #1
Your List of Ingredients
About 8 Popsicle sticks
Objects for launching (mini marshmallows, pom-poms, beads, etc.)
Step 1: Decorate the Popsicle sticks
This step is optional, but we enjoyed decorating a few popsicle sticks before setting up our catapult. We used markers, but paint would work as well! Let them dry before starting.
Step 2: Create the Framework
Start by stacking about 5-10 popsicle sticks together and secure either end using rubber bands.You can experiment later with how tall to make this stack. Will its height change the motion of your projectile? Next, align one popsicle stick with a plastic spoon and secure the end with a rubber band. This rubber band will provide the tension needed for launching projectiles.
Step 3: Assemble the catapult
To assemble to catapult, slide the popsicle stick that is connected to the spoon between the bottom two popsicle sticks in the stack. Doing this will create an X shape. The spoon will be angled and will hold your projectiles and serve as the launching mechanism. You can secure the spoon to the stack of popsicle sticks further by wrapping another rubber band around them.
Step 4: Ready to launch!
Place an object such as a mini marshmallow or pom-pom in the spoon. With one hand, hold the stack of popsicle sticks to secure the catapult, and with the other push down on the spoon, then release!
Catapult #2
Your List of Ingredients
16 Rubber bands
Objects for launching (mini marshmallows, pom-poms, beads, etc.)
Step 1: Decorate the Popsicle sticks
This step is optional, but we enjoyed decorating a few popsicle sticks before setting up our catapult. We used markers, but paint would work as well! Let them dry before starting.
Step 2: Create the Framework
Start by making two X shapes with the popsicle sticks with the intersection closer to one side. Secure with rubber bands. Next, use 4 more popsicle sticks to make a square, allowing the ends of the popsicle sticks to extend out a little.
Step 3: Assemble the catapult
Take your two X shapes and secure them to the inner corners of the square. Place one popsicle stick on top of the X shapes so that it extends between them and holds them upright. Secure with a rubber band on each side. Next take a new popsicle stick and loop a rubber band around one end a few times. Pull a couple loops out and wrap them around the other stick as shown in the video below, then hook the rubber band loops back over itself on the other side so it is secured. Do the same thing to the other side. Make sure this popsicle stick is facing the same direction as the one above it that's resting on top of the X shapes.
Step 4: Attach the lever
Next, take a plastic spoon and place the bottom in front of the lower popsicle stick and the top end behind the top popsicle stick. Take a rubber band and loop it around the base of the spoon and then secure it to the backside on both sides of the square base, as shown in the video above. Use two rubber bands here for better tension and support. Bend the spoon down, add an item to launch, then start your target practice!
Activities to Explore with Your Catapult
Now that you have your catapult ready to launch, here are some fun activities you can engage in:
Target Practice
Set up targets, such as cups, cardboard structures, or even small objects, at various distances. Challenge yourself to hit the targets by adjusting the angle and force of your launches. Experiment with different projectile weights and observe how they affect accuracy and distance.
Distance Competition
Measure the distance your projectiles can travel and engage in a friendly competition with friends or family members. Mark a starting point and see who can launch their objects the farthest. Use different launching techniques, adjust the tension in the rubber bands, and vary the angle to optimize your launches.
Science Experiments
Use your catapult to conduct science experiments. Explore the effects of variables like projectile weight, rubber band tension, or spoon angle on the distance or trajectory of the launched objects. Keep a record of your observations and analyze the data to draw conclusions about the relationship between these factors.
Artillery Challenge
Design a simple structure, such as a miniature castle or tower, and attempt to knock it down with your catapult. Test your precision and aim by strategizing how to hit specific parts of the structure. You can even create a scoring system to make the challenge more competitive.
Catapult Design Iterations
Once you've become familiar with the basic catapult design, challenge yourself to improve it further. Experiment with different materials, modify the angles, or add additional components to enhance its performance. See if you can launch projectiles with more accuracy, distance, or speed.
Embrace your creativity, curiosity, and problem-solving skills as you explore these catapult activities. Let the joy of discovery and friendly competition fuel your enthusiasm for learning and experimentation.
Enjoy your catapult adventures and have a blast!
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