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