Project: Catapult Launch Angles

thingiverse

I have designed this project to be a hands-on way for students to demonstrate launching projectiles at fixed angles. The catapult features an adjustable stop pin that can be set in 5° increments from a 25° angle to a 90° angle. The throwing arm has a maximum tension indicator (stop) to help students achieve equal tension on every launch, allowing them to compare the distance covered when changing the launch angle. https://youtu.be/tsxN56f2HFo How I Designed This Project I began by researching the strength of plastic and determined that a 3x3-4x4mm bar would be an ideal stop size. Next, I created an arc of 4x4mm holes with about 3mm of material in between them for added strength using AutoCAD. After finalizing this design, it served as the basis for the catapult's structure. I then exported a DXF file and imported it into Fusion 360, where I worked on designing the side frame of the catapult. Once I was satisfied with one side, I created the front attachment support, bottom support, stop bar, and finally the throwing arm. After printing each component, I conducted a test. The original throwing arm had some flaws that required revisions before arriving at a design I was happy with. Started with a sketch of the stops in AutoCAD Fusion 360 - Design of the side Overview and Background Projectile physics and trajectory are the main focus of this project. The goal is to help students grasp these concepts through practical application and physical testing. Lesson Plan and Activity Step 1 - Background Knowledge Ask students to write down what they predict will happen based on the catapult. Discuss vectors Discuss gravity Discuss friction and air resistance Discuss projectile physics Discuss trajectory Print and use catapult as a discussion aid Step 2 - Design / Build Option 1: Print catapult as is from Thing files Option 2 (bonus): Have students design a projectile to launch Option 3 (alternate / advanced): Have students design a catapult to meet the criteria. Have students print their catapult. Step 3 - Practical Testing Find a suitable firing range. Setup a firing line and lay out a grid for determining range. Assemble catapult as shown in the video. Fire 2-3 shots (or more) at each angle from 25° to 90° with 5° increments Measure each shot and record data **NOTE: Ensure each shot is the same. The tension stop was added to the throwing arm for this reason. Option 3 from above: Hold a contest to determine who met your launching criteria with their design. Step 4 - Calculations Find the average shot range for each angle (assuming multiple shots were taken) Plot data Determine the optimal angle for firing conditions. Step 5 - Review Review data Discuss results and why they happened. Did the answer to the best angle vary from 45°? Why? What could we do differently? What are real-world applications of projectile physics? (beyond pumpkin chunkin or military) How did results compare to what students wrote down at the beginning? Materials Needed Accessories The following materials and items can be helpful with this project. Rubber bands for powering catapult Projectile (students could design one as an optional add-on) Measuring device - for calculating distance Pencil and paper - for taking notes on results Safety gear - projectiles involved! Skills Learned Projectile physics Trajectory Vectors Gravity Rubric and Assessment How does gravity affect the projectile? How does friction affect the projectile? What are vectors? What is the optimal launch angle with no wind? References https://en.wikipedia.org/wiki/Projectile https://en.wikipedia.org/wiki/Trajectory