7.3 Solving Pulley Systems
One of our classic problems to analyze using Newton's second law is the motion of two blocks with a rope that's wrapped around a pulley. So imagine we have a pulley, P, and we hang from that block 1 and we hang from that block 2. The pulley is suspended by another rope, and it's attached to a wall. And let's now try to use Newton's second law to analyze this motion. Now, going back to our methodology, the first thing we want to ask ourselves is to identify what are all the moving pieces? So I'm going to make my first assumption here, that the rope/pulley a surface so that's right here is frictionless. Now, what that assumption means is that the pulley will remain at rest. And therefore, when we want to break this problem down, our first question is to identify all the moving objects. And so we really have three. We have mass, which we label by 1, 2, and the rope. So our goal now is to identify all the moving objects and to draw free body force ...