Articoli correlati a Elements of natural philosophy, elementary statics...
Sinossi
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1862 Excerpt: ...if the horse be disturbed a little from the horizontal position, it will always move back towards that position again, and thus imitate the action of galloping by swinging backwards and forwards without falling off the stand. The difficulty of balancing a long pole, A B, on the finger A, fig. 132, is an illustration of unstable equilibrium. The centre of gravity Fig. 132. G of the pole, is above the point of support A, and therefore, though the pole will rest where the line G A is truly vertical, it will, on any inclination from the vertical position, fall quite away from that position, unless, by a quick motion of the finger, the point of suppport A is moved about so as to keep it exactly under G. The difficulty of thus balancing the pole on the finger arises from the fact, that the very least disturbance of the pole out of the exact vertical position of equilibrium, causes it to fall quite away from that position, unless the point of support be moved in such a way as to arrest the fall. A child learning to walk is an illustration of this attempt to balance a body, supported on such a small base as the feet are. The child has to learn by experience, though it be not aware of the fact, that, when it stands, the vertical through its centre of gravity must fall within the limits of its feet; and it takes much time and practice to habituate the muscles to keep the body, by an involuntary effort, always in such a position that the vertical through the centre of gravity may not fall without the limits of the feet. Considering the variety of attitudes into which the body is thrown in actions of standing, walking, running, &c., it is not surprising that some practice is necessary to enable a child to fulfil, in an involuntary manner, the mechanical law we are ...
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