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Inertia

المؤلف:  GEORGE A. HOADLEY

المصدر:  Essentials of Physics

الجزء والصفحة:  P-17

2025-10-19

478

Is the tendency a body has to retain its condition of rest or motion. Whenever a body is at rest, it can be put in motion only by some force outside of itself; and whenever a body is in motion, the rate or direction of this motion can be changed only by the application of a force from without the body. This property is, therefore, purely negative. Demonstration. - Place a smooth flat card on the mouth of a bottle with a small neck, and on it put a small marble exactly over the mouth. of the bottle. A snap with the finger on one corner of the card will send it spinning across the room, while the ball will drop into the bottle. Place a little cotton inside the bottle.

Inertia is illustrated in a great many accidents: for example, the spilling of a liquid in a dish that is moved too quickly; the shock to a railway passenger when the air brakes are applied too suddenly; the fall caused by jumping from a rapidly moving car.

Use is made of inertia, as in driving on the head of a mallet by striking the end of the handle; throwing an apple stuck on the end of a rod; or changing the position of a column of mercury in a glass tube by jerking the tube lengthwise.