Pressure depends on the density and height of a liquid column, and not on the shape of the container or total volume of liquid.
Pressure acts in all directions.
Units: d= [kg.m*), h = (m), P = Nm*1 = (pascal,
abbreviated to [Pa).
Atmospheric Pressure🔥
The earth is surrounded by an air belt which is often referred to as the atmosphere.
The atmosphere is several kilometres high.
Atmospheric pressure is the weight of air which is supported by a unit area of the earth's surface.
Its value is approximately 1.013 x 105 Pa, and this is referred to as 1 atmosphere.
The atmospheric pressure of 1 atmosphere is equivalent to the pressure which will be exerted at the bottom of a mercury column of height 760 mm or a water column of height 10.3 m.
Atmospheric pressure decreases with altitude: its value on the top of a mountain, for instance, is less than at sea level.
Pressure acts in all directions.
Units: d= [kg.m*), h = (m), P = Nm*1 = (pascal,
abbreviated to [Pa).
Atmospheric Pressure🔥
The earth is surrounded by an air belt which is often referred to as the atmosphere.
The atmosphere is several kilometres high.
Atmospheric pressure is the weight of air which is supported by a unit area of the earth's surface.
Its value is approximately 1.013 x 105 Pa, and this is referred to as 1 atmosphere.
The atmospheric pressure of 1 atmosphere is equivalent to the pressure which will be exerted at the bottom of a mercury column of height 760 mm or a water column of height 10.3 m.
Atmospheric pressure decreases with altitude: its value on the top of a mountain, for instance, is less than at sea level.
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The Siphon🔥
- The siphon is a bent tube used for transferring liquid from one container to another one at a lower level.
The tube is first filled with the liquid to be transferred, and the liquid is allowed to drain from the right arm (XB) under gravity, thus creating a vacuum in XB.
More liquid is then forced into the tube by atmospheric pressure acting at A, thus ensuring continuous flow of liquid.
The liquid flows under a pressure difference hdg, which means that B must be lower than A in order for the siphon to continue functioning.
• The operating principle of the siphon is made use of in the modern toilet's water cistern and in drawing liquid from a reservoir which is not easily acces sible.
- The siphon is a bent tube used for transferring liquid from one container to another one at a lower level.
The tube is first filled with the liquid to be transferred, and the liquid is allowed to drain from the right arm (XB) under gravity, thus creating a vacuum in XB.
More liquid is then forced into the tube by atmospheric pressure acting at A, thus ensuring continuous flow of liquid.
The liquid flows under a pressure difference hdg, which means that B must be lower than A in order for the siphon to continue functioning.
• The operating principle of the siphon is made use of in the modern toilet's water cistern and in drawing liquid from a reservoir which is not easily acces sible.
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7 Measurement of Pressure
A manometer is used to measure gas pressure.
The gas is admitted to one end of a U-tube which is partly filled with a liquid of density d while the other end of the tube is open to the atmosphere
If the liquid in the open arm rises to a height h above that on the other arm, the pressure of the gas is P= Pa+hdg
where Pa is the atmospheric pressure.
A manometer is used to measure gas pressure.
The gas is admitted to one end of a U-tube which is partly filled with a liquid of density d while the other end of the tube is open to the atmosphere
If the liquid in the open arm rises to a height h above that on the other arm, the pressure of the gas is P= Pa+hdg
where Pa is the atmospheric pressure.
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Relative Density🔥
The relative density, R.D. (or specific gravity) of a substance is the ratio of the density of the substance to the density of water.
If d= density of substance and dw= density of water, Relative Density= density/dw
The relative density of water is 1.0.
All metals and most solids have R.D. greater than 1, while air and several liquids have R.D. less than 1.
Units: R.D. bears no units.
The relative density, R.D. (or specific gravity) of a substance is the ratio of the density of the substance to the density of water.
If d= density of substance and dw= density of water, Relative Density= density/dw
The relative density of water is 1.0.
All metals and most solids have R.D. greater than 1, while air and several liquids have R.D. less than 1.
Units: R.D. bears no units.
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Seawater has specific gravity of 1.03. Neglecting the atmospheric pressure, the force exerted by scawater on the hatch door of a submarine of area 0.8 m? at a depth of 300 m is
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Let’s attempt this ✨
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Oil of mass 0.5 g and relative density 0.5 forms a thin film of area 0.25 m' on the surface of water. The thickness of the oil film is
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Attempt everyone ✨
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Upthrust and Archimedes' Principle🔥
An object immersed in a liquid experienccs an upward force which is called the upthrust or buoyancy.
The upthrust is due to the difference in pressure between the upper and the lower faces of the object, the pressure being greater at the lower face.
Archimedes' principle states that a body immersed in a fluid experiences an upward force (upthrust) which is equal to the weight of the fluid displaced.
Any immersed body thus experiences two forces
its true weight(I) acting vertically downward, an
the upthrust (Fu) acting vertically upward.
An object immersed in a liquid experienccs an upward force which is called the upthrust or buoyancy.
The upthrust is due to the difference in pressure between the upper and the lower faces of the object, the pressure being greater at the lower face.
Archimedes' principle states that a body immersed in a fluid experiences an upward force (upthrust) which is equal to the weight of the fluid displaced.
Any immersed body thus experiences two forces
its true weight(I) acting vertically downward, an
the upthrust (Fu) acting vertically upward.
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