4:92 NICHOLLS'S SEAMANSHIP ANP NAUTICAL KNOWLEDGE

The resistance of the water to the movement of the blade is the

fulcrum.

Arm X weight = arm X power.

8 W = 12 X 100, W = 150 Ibs.
The propelling force is 150 Ibs. on each rowlock.

Fig 7.

In levers of the third class the power is between the weight and the
fulcrum (Figure 8).

Example.—Up-ending a ladder. The foot of a ladder is fixed to the
ground, the other end 30 feet up is leaning on a wall with a pressure

Fig. 8 —Lever. Third Class.
of 10 Ibs. A man takes hold of the ladder 5 feet up from the foot;
what power must he exert to pull the top end away from the wall?
Arm X power = arm X weight
5 P=^30 X 10 /. P = 60 Ibs.
The man must exert a pull of 60 Ibs.