# Science AHSGE Standard VIII Objective 2- Pressure in Fluids.

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Science AHSGE Standard VIII Objective 2- Pressure in Fluids

Pressure Amount of force applied to an area –Pressure = Force / Area –Metric unit of pressure- Pascal (Pa) One newton per square meter –Common units include: Atmospheres (Atm) Pounds per square inch (PSI)

Atmospheric Pressure As you increase in elevation (distance above sea level), air pressure decreases –Its harder to breath at the top of a mountain because the air is thinner As you down in elevation, air pressure increases Your ears pop as you go up or down in elevation or altitude (distance up in the air) in order to equalize pressure within your body with that outside

Atmospheric Pressure

Lungs and Air Pressure Air flows into and out of lungs when air pressure in the alveoli (lung sacs) differs from that of the surrounding air –Higher alveoli pressure = exhale –Lower alveoli pressure = inhale

Water Pressure Downward pressure of water is equal to the weight of the column of water above an objects surface area –The deeper you go, the greater the pressure –When diving, ears also pop to equalize body pressure Water pressure in local water sources increases with the height of the water tower –The higher the tower, the faster the water movement due to gravity = higher water pressure

Water Pressure

High Pressure Gases in Liquids –When liquid pressure is lessened, the gas is released as bubbles –Ex: Open a can of coke- Fizzes –Ex: The Bends- Painful condition caused by a build up of nitrogen gas in the body while surfacing too fast from a dive

Turgor Pressure Fluid pressure inside a cell that keeps cell from collapsing in on itself –Dehydration- Loss of turgor pressure Cell shrivels Wilting in plants –Too much turgor pressure can cause cell to burst

Blood Pressure The measurement of force applied to the walls of the arteries as the heart pumps blood through the body –Determined by the force, the amount of blood pumped, and the size and flexibility of the arteries –Systolic pressure- as heart beats; Diastolic pressure- between heart beats Normal 120/80 –Which artery will have the lowest blood pressure? Highest? AB C D

High Blood Pressure Hypertension- Chronic high blood pressure –Can be genetic –Most characterized with blockages Stroke- Interruption of blood supply and oxygen to an organ –Results in tissue damage –Common to brain –Caused by either bleeding or blood clots Fatty deposits and platelets collect on the walls of arteries

High Blood Pressure Anuerysm- An abnormal widening or ballooning of a portion of an artery –Can be congenial (present before birth) –Can be caused by high blood pressure or blockages

Pascals Priciple Pressure applied at any point inside a closed system with a confined fluid will transmit equally throughout the fluid –Ex: A balloon is a closed system; applying pressure on one end will cause the same pressure throughout the balloon –Ex: Hydraulic systems are closed, confining either a gaseous or liquid fluid. Pressure applies to the smaller input piston first (F1 and A1) and transmits to the larger output plunger second (F2 and A2) Remember: Pressure = force/area –Force is measure in newtons –Area is measured in cm² or m²

Try this! A force of 200 newtons is applied to the piston of 0.15 square meters, while a force is released from the 0.75 square meter plunger. What force is exerted from the plunger?

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