This experiment teaches the students about the scientific method, especially about constants and variables. We make the pendulums out of small paper cups, string, and bent paper clips. We attach the string to a ruler and let the whole thing hang off the edge of a desk. We use 1 cm place value cubes for "weight". Incidentally, the "ones" blocks have a mass of about 1 gram. Use a half-circle protractor held upside down to measure the pull back angle. This is a very easy and straight forward experiment with obvious results that ensure success for all. Great for an adapted version of a science fair project as well. Spoiler alert – only changing the length of the string will change the swings per minute!