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A change in the pressure applied to a fluid is transmitted undiminished to every point of the fluid and to the walls of the container. In simpler words it can be stated as “the pressure applied to an enclosed fluid is transmitted equally to all points of the fluid and therefore to all walls of the vessel containing the fluid. Hydraulic press is a very good obvious example for this law/ principle. It is shown below:
Since the pressure must be same everywhere:
Pat1 = Pat2
Since pressure = force / area, thus, F1/A1 = F2/A2 or F2 = (F1/A1) × A2. Therefore, the force at the outlet (2) is augmented by the size of the area of the outlet!
Archimedes’s Principle
When an object is partly or wholly immersed in a fluid, it is exerted by an upward force called buoyant force. The magnitude of the buoyant force is equal to the weight of the fluid displaced by the object. This is called Archimedes’s principle. It can be noted that the buoyant force acting on the object is always in the vertically upward direction and through the center of gravity of the displaced fluid. And, this principle is valid as long as the surface tension on the body is neglected.
• The weight of the fluid displaced is directly proportional to the volume of the displaced fluid. Thus, among objects with equal masses, the one with greater volume has greater buoyancy.
• If the density of an object is greater than the density of the fluid, then the upward buoyant force is less than the downward force of gravity and the unsupported object sinks.
• At neutral buoyancy the buoyant force is balanced by its weight.
• An object’s buoyancy reduces with the compression of the fluid and increases with the expansion of the fluid.
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