I designed this lab for the conservation of energy unit in my physics class. Sadly, my school has no materials for physics labs. Therefore, this lab activity uses only dental floss, thumbtacks, beads or other masses, graph paper, and timers (cell phone timers are great)!
In the lab, students first calculate the theoretical average speed of a pendulum and then compare this to their measured average speed. The lab is very short. The set-up and measurement can be done in about 30 minutes. Also, students are able to achieve very low percent errors in the lab!