The simplest form of lever in common use is a steel rod known as a crowbar, but the term lever may be applied to any rigid body which is pivoted about a point called the fulcrum. Levers are based on the principle of moments, which was discussed in
chapter 6. A force called the effort is applied at one point on the lever, and this overcomes a force called the load at some other point. Incidentally, the terms effort and load are not restricted to levers but apply to all types of machine. Fig. 8.1 illustrates some simple machines based on the lever principle.