Ballistic Pendulum (To Measure Speed of NERF Dart)

thingiverse

This is a ballistic pendulum. It is constructed of 3D printed parts, 1/4" wooden dowels, and string. Its purpose is to measure the speed of NERF darts and other small, low speed projectiles. This is a MakerEd Challenge 2.0 entry. To use: Shoot a dart at the pendulum. Measure how high it swings. Calculate the gravitational potential energy from "mgh". Use that to calculate the kinetic energy of the dart, "KE", which is 0.5mv^2. Solve for v to get the speed. See handouts for more information. Test of the prototype: https://youtu.be/BXyvUQC2mLQ How I Designed This The connectors were designed in TinkerCAD. The bolt and threaded hole were made using mike_linus' "NUT JOB" customizer. The rest of this was designed using 123D design from AutoDesk. Project: Ballistic Pendulum (To Measure Speed of NERF Dart) Project Name Ballistic Pendulum (To Measure Speed of NERF Dart) Overview & Background Students will learn how to use physics and math (and optionally engineering) to measure the speed of a NERF dart. Objective By completing this project, students will learn about kinetic energy and potential energy. They will also learn how to calculate mean, median, mode, and standard deviation. There are engineering / design exercises that are optional as well. Audiences This project is suitable for anyone learning physics, math, or engineering. It is also a fun way to introduce kids to STEM. Anyone who likes NERF guns should also enjoy the project. Skills Learned / Standards The skills learned in this project include: setting up and performing an experiment; calculating statistics; and basic engineering / design skills. Lesson / Activity After the ballistic pendulum is assembled, students will come up with a way to measure how high the coin box will swing. Then they will fire a dart at it. Once they have obtained the height, they can calculate the velocity of the dart. The coin box can be loaded with coins to make it heavier if it swings too high when empty. Or if it doesn't swing high enough to measure easily, the lid and bolt can be removed. Cardboard or Velcro can be used to make the darts stick to the box. See handouts for more information. Duration About one hour or less. Preparation Students should know some basic math and a little bit of physics. They will also need a dart gun and darts, as well as some way to measure the height of the swinging coin box (a ruler, graph paper, a marker, a smartphone, etc.). A piece of cardboard with tape inserted into one of the slots on the coin box will make suction cups stick to the box. A small piece of Velcro will make Velcro darts stick. A calculator (or smartphone calculator app) is necessary to carry out the math. References https://en.wikipedia.org/wiki/Ballistic_pendulumhttps://en.wikipedia.org/wiki/Standard_deviation Rubric & Assessment By the end of this project, students should have assembled a ballistic pendulum. They should have taken ten height measurements and calculated ten velocities. They should have completed the calculations handouts, which includes calculating the mean, median, mode, and standard deviation. They should also have done some critical thinking about the experiment. Handouts Handout 1: Instructions. Handout 2: Discussion. Handout 3: Calculations.