Description of the apparatus

 

The catapult is based on an ancient design.This catapult was built entirely out of 2X4, cotton rope and a wooden dowel in and aluminum sleeve.First the frame was built.It is rectangular in the dimensions of 1X2 feet.Then 2 towers were added, and across an arrestor bar was placed, also made of 2X4.The purpose of this arrestor bar is to stop the swing arm in its travel and release the payload.2 supports were put in place to support the tower, but werenít really necessary.Then, around the towers, through the frame, holes were drilled to pass 2 ropes through.These ropes attached to the swing arm, which was made of hardwood dowel.They were wound up, such that they were creating tension, and then held in place by the arrestor bar.Here was where the aluminum sleeve came in handy, because the swing arm length was bigger than the frame.So to wind up the catapult, we wound the sleeve, which was 9 inches long, and then inserted the swing arm.Finally, to mount the photogates, I added two brackets on the towers, but since the catapult was pretty deadly, it always jarred them loose, and our timer was messing up.To fix this, we mounted the photogates and lasers on lab stands.Donít believe me?Check out the picture:

 

Mounting the photogates on the project. We later figured out this wouldn't work, so they were moved to lab stands.