490

NICHOLLS S SEAMANSHIP AND NAUTICAL KNOWLEDGE

of levers, first, second, and third class. The foregoing illustration is
that of a first class lever by simply substituting the term Power for one
of the weights. The relative positions of the fulcrum, weight and power
determine the class of lever.

In levers of tlie first class the fulcrum is between the weight and the
power (Figure 4).

Fig 4 —Lever Fust Class

Example.—Tilting up a heavy weight to get a cargo sling under it.
A man puts his weight of 150 Ibs. on the end of a lever 6 feet from the
fulcrum, the other end of the lever 2 feet on the other side of the fulcrum
is under a box. The man is just able to tip the box, what weight is it?
Arm X weight = arm X power
2 W = 6 X 150 Ibs.

W = 450 Ibs.

The weight of the box is therefore 900 Ibs. as half its weight, 450 Ibs.,
is supported by the corner resting on the floor, and half is supported
by the lever.

v/

Fig. 5.

S&ample.—A steelyard. What must be the weight or power ol