UKPCS Science: Pressure #12

Oracle IAS, the best coaching institute for UPSC/IAS/PCS preparation in Dehradun brings to you UKPCS Science (paper #6- Pressure

Pressure is defined as force per unit area. It is usually more convenient to use pressure rather than force to describe the influences upon fluid behavior. The standard unit for pressure is the Pascal, which is a Newton per square meter.

Atmospheric pressure, sometimes also called barometric pressure, is the pressure within the atmosphere of Earth (or that of another planet). In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation.

Atmospheric pressure is caused by the gravitational attraction of the planet on the atmospheric gases above the surface. The standard atmospheric pressure is 760 mm of Hg. The height is measured from the mean sea level.

Hydrostatic pressure is the pressure that is exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above.

Real life utility of:

Hydrostatic pressure:

1) By holding large amounts of water back behind a dam, and then letting it  spill slowly thru turbines, electricity can be generated thanks to  hydrostatic pressure.

2) Another way to use hydrostatic pressure, is by building a water tank that  is sitting very high up.

3) At hospitals, where a  patient has a catheter (the clear plastic bag with water and nutrients)  and this catheter is placed much higher up than the patient, so  hydrostatic presure will push the water and nutrients into the patient’s bloodstream.

Atmospheric Pressure:

• inflating tires
• playing musical “wind” instruments
• drinking through straws
• flushing toilets
• vacuum cleaner

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