| Share page | Visit Us On FB |
|
III. §37.] ACCUMULATED IMPULSES. |
73 |
||
|
exposed to the influence of its sounding fellow, hardly any appreciable result ensues. The resonance, when produced, is at first extremely feeble, and gradually increases in intensity under the continued action of the originally-excited fork. Some seconds must elapse before the maximum resonance is attained. The conditions of our experiment show that the resonance of the second fork was , due to the transmission by the air of the vibrations of the first, the successive air-impulses falling in such a manner on the fork as to produce a cumulative effect. If we bear in mind the disproportionate mass of the body set in motion compared to that of the air acting upon it,—steel being more than six thousand times as heavy as atmospheric air for equal bulks— we cannot fail to regard this as a very surprising fact. Let us examine the mechanical causes to which it is due. Suppose a heavy weight to be suspended from a fixed support by a flexible string, so as to form a pendulum of the simplest kind. In order to cause it to perform oscillations of considerable extent by the application of a number of small impulses, we proceed as follows. As soon as, by the first impulse, the weight has been set vibrating through a small distance, we take care that every succeeding impulse is impressed in the direction in which the weight is moving at the time. Each impulse thus applied will |
|||