Ques. In fig. 1,311 what is the line AD called?
Ans. The resultant, that is, it represents the actual movement of the boat resulting from the combined forces of wind and tide.
Ques. What are the forces, AB and AD in fig. 1,311, represented by the sides of the parallelogram, and which act upon a body to produce the resultant, called?
Ans. The components.
Fig. 1,312.—Parallelogram of forces; method of obtaining the resultant of two components acting at right angles.
EXAMPLE.—Two forces, one of 3 lbs. and one of 4 lbs. act at a point a in a body and at right angles, what is the resultant?
Take any convenient scale, say 1 in. = 1 lb., and lay off (fig. 1312.) AB = 4 ins. = 4 lbs.; also, AC (at right angles to AB) = 3 ins. = 3 lbs. Draw CD and BD parallel to AB and AC respectively, and join AD. The line AD is the resultant of the components AB and AC, and when measured on the same scale from which AB and AC were drawn will be found to be 5 inches long, which represents 5 lbs. acting in the direction AD.
Circuits containing Resistance and Inductance.—In circuits of this kind where the impressed pressure encounters both resistance and inductance, it may be looked upon as split up into two components, as already explained, one of which is necessary to overcome the resistance, and the other, the inductance. That is, the impressed pressure is split up into