16

LESSON

Solving Lever

Problems

One of the oldest machines known to humans is the lever. The principles of

the lever are studied in physics. Most people are familiar with the simplest

kind of lever, known as the seesaw or teeterboard, often seen in parks.

The lever is a board placed on afulcrumor point of support. On a seesaw,

the fulcrum is in the center of the board. A child sits at either end of the

board. If one child is heavier than the other child, he or she can sit closer

to the center in order to balance the seesaw. This is the basic principle of

the lever.

In general, the weights are placed on the ends of the board, and the

distance the weight is from the fulcrum is called the length or arm. The basic

principle of the lever is that the weight times the length of the arm on the left

side of the lever is equal to the weight times the length of the arm on the right

side of the lever, orWL¼wl. See Figure 16-1.

172

Copyright © 2005 by The McGraw-Hill Companies, Inc. Click here for terms of use.