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Transmission of Pressure by Liquids

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-129

2025-11-08

470

Whenever pressure is brought to bear upon a solid, the molecules, being unable to move freely over one another, will transmit the pressure, undiminished, in one direction only. In the case of liquids, however, the free movement of the molecules over one another secures the transmission of pressure, without change, in all directions.

Demonstration. - To a thin glass bottle fit a straight cork, of such a size as to go into the neck snugly. Fill the bottle with water. Insert the cork and bring pressure to bear upon it by a lever, as in Fig. 1. The shattering of the bottle shows that the pressure was transmitted in all directions.

The action of the molecules of a liquid in transmitting pressure may be illustrated by filling a bottle with peas and pressing upon the top layers. Since each pea does not lie directly upon another, but in a depression left between those in the next lower layer, a vertical force acting upon any pea will be resolved into other forces in the direction of the points of contact between it and the peas which it touches.