Suspend a stick with a hole at its center as in Figure 98, and hang a 4-pound weight at a distance of 1 foot from the fulcrum, supporting the load by means of a spring balance 2 feet from the fulcrum. The pointer on the spring balance shows that the force required to balance the 4-pound load is but 2 pounds.
The force is 2 feet from the fulcrum, and the weight (4) is 1 foot from the fulcrum, so that
Force × distance = Weight × distance,
or 2 × 2 = 4 × 1.
FIG. 99.—The wheelbarrow lightend labor.
Move the 4-pound weight so that it is very near the fulcrum, say but 6 inches from it; then the spring balance registers a force only one fourth as great as the weight which it suspends. In other words a force of 1 at a distance of 24 inches (2 feet) is equivalent to a force of 4 at a distance of 6 inches.
FIG. 100.—A modified wheelbarrow.
One of the most useful levers of this type is the wheelbarrow (Fig. 99). The fulcrum is at the wheel, the force is at the handles, the weight is on the wheelbarrow. If the load is halfway from the fulcrum to the man's hands, the man will have to lift with a force equal to one half the load. If the load is one fourth as far from the fulcrum as the man's hands, he will need to lift with a force only one fourth as great as that of the load.
This shows that in loading a wheelbarrow, it is important to arrange the load as near to the wheel as possible.