Simple Machines

In the Introduction, we gave the spade as an example of a simple machine. It hardly seems to be a machine at all,but it does have something in common with all machines- it help you perform a task -digging- more easily than you could without it.More technically, the spade increases force you put into the digging action. To turn over the soil, you push down on the handle. We call this force the effort. The spade is designed so that it magnifies this effort into a more pow- erful force, which lifts up a spadeful of soil (a weight called the load).The spade is an example of a kind of simple machine called the lever. In this chapter we look at the principles behind the lever and the five other kinds of devices scien- tists recognize as simple machines. They they are the inclined plane, the wedge, the screw, the wheel and axle, and the pulley . We also look at gears which we can think of a use- ful modifications of th wheel.