MadSci Network: Engineering |
Dear Sara: I must say, that at first I was a little confused by your question. A lever is a lever, and there can be only one! But after thinking about it a little, (and nosing around on the web) I began to understand what your meant, and also your confusion. (which was mine, too, at first!) So let's forget rules and types for a bit and try to understand what a lever is, exactly. A lever is, quite simply, a way to do work. You move one end and another end moves. Since you don't get something for nothing in this world, you're only going to get as much work out of a lever as you put into it. That is the key concept to understanding levers. Not so bad, is it? So how does a lever work? You are correct that there are three key items to a lever: the fulcrum, the ``force'', and the ``resistance''. Saying ``force'' and ``resistance'' are part of the lever is a little confusing because they are not actually part of the lever itself, but we'll get to that a little later. The fulcrum, or pivot, has one purpose: to give you something to push against. Without it, you might as well be beating the problem with a stick. While this may be very personally satisfying, it's not very effective in getting work done. The ``force'', as you call it, is simply the work you put into the system. The ``resistance'' is the work you get out of the system. Since you seem familiar with the ``rules'' of levers, I won't bore you with details of how they relate to each other, I just wanted to give you another way of thinking of things that might help. An excellent description of the so-called types of levers can be found at http://beakman.com/lever/lever.html a> but it it simple enough to say that the only thing that is different between these types of levers is where the force is applied and where the work is done in relation to the fulcrum. The exact same rules apply for all types, it's just that you're looking at different parts of the lever. As for your specific question about a baseball bat, I can see your confusion. A baseball bat, by itself, isn't a lever, it's a stick. But when you pick it up in your hands and swing it, it becomes a lever. How? Your shoulders become the fulcrum (the thing the lever swings around), the baseball becomes the resistance (the thing you're trying to move), and your muscles supply the force. In the words of the website I mentioned above, it becomes a 'third class' lever. I hope this helps you understand things a little bit more! -m Michael Pantiuk mpanti1@umbc.edu --------------- This calls for a subtle combination of mathematics and extreme violence.
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