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Simple Machines
By Sharon Fabian 		  
1     Machines make work easier. When a caveman had to move a rock that was too heavy to lift, he might have used a big stick to make it easier. A long, long time ago, someone invented the wheel, and that made things a lot easier. By the Industrial Age, people were inventing all kinds of machines. New vehicles and new factory machines made life easier and gave people free time that we never had before. We really liked these inventions that made our lives easier! People are still creating new machines all the time. There is something really fun about inventing a contraption that seems to do some of our work for us.
 
2     Machines make work easier. So to understand machines, you first have to know what the work is, scientifically speaking. Maybe you define work as carrying out the garbage, raking leaves, or cleaning your room. These are all forms of work, but scientists have a more, well, scientific definition. To them, work is using a force to move an object across a distance.
 
3     There is a mathematical formula for this: W = F x D. It means "work equals force times distance."
 
4     Machines make it possible to move larger objects, or to move objects faster or farther. Machines make work easier by adjusting the force or the distance to your advantage. They are used to push, pull, and lift. A machine can be used to increase the force or the distance, but not both. To get more force, you have to give up some distance. To get more distance, you have to give up some force. It's a scientific law called Conservation of Energy.
 
5     Machines let you do more with less muscle power. When a machine is used to increase force, that is called mechanical advantage. For example a jack used to lift a car has a lot of mechanical advantage. So does a crane used to lift a heavy steel beam. A hammer used to pound in a nail has mechanical advantage too.

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