Lever Demo

Simple machines provide users with a benefit called Mechanical Advantage (MA), but only with a Tradeoff or off-setting cost. Some machines offer the advantage of multiplying the Applied Force with a Tradeoff that the AF must travel a greater distance. Others multiply the distance the AP travels, but only with a proportional reduction in the AF. Making these ideas real and memorable to students are two goals of science teacher Earl Carlyon's demonstration of a first-class lever.

From your standpoint as a teacher, you might evaluate how well MOVIE 1's demo seems to go. Listen carefully to the questions Earl embeds in the demo that addresses student misconceptions about lifting forces and gravity. Note the misconceptions that appear in students' statements (e.g., at least one student thinks that if a person tries to lift something but is not successful, then no force has been applied), and how Earl addresses each. Look also for how Earl choreographs his demo with safety in mind.