Pressure under the water

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Problem# h2phy1 - Pressure converted inside the Aorta

Problem# h2phy2 - Pressure inside vein

Problem# h2phy3 - Pressure on the floor

Problem# h2phy4 - Pressure under the sea

An enterprising diver reasons that if a typical 20 cm.
long snorkel tube works, a 6.0 m. long tube should
also. If he foolishly uses such a tube, what is the pressure
different Δp between the external pressure
on him and the air pressure in his lungs? Why is he in danger?

Strategy - the rule "Must have" of Mr.Zhang ®

Absolute pressure (P) The difference between absolute pressure and atmospheric pressure is called gauge pressure. P =  (Pg) + (Po) Absolute pressure - Atmospheric pressure = Gauge pressure       Material or Object         Density (kg/m3)     Water: 20 οC and 1 atm 0.998x103 Sea water: 20 οC and 1 atm 1.024x103   1 atm = 760 mmHg = 760 torr = 29.9 in.Hg =101.325 kPa = 14.7 lb/in.2

Solution The diver at depth L = 6.0 m without the snorkel tube. The external pressure on him is given by ; P =  Po + ρgh ΔP=P-Po=ρgL ; because L=h     =(1000 kg/m3)(9.8 m/s2)(6.0m)     =5.9x104 Pa ∴The pressure difference is about 0.6 atm, is sufficient to collapse the lungs and force the still pressurized blood into them,a process known lung squeeze. "thoracic squeeze, also called Lung Squeeze, compression of the lungs and thoracic (chest) cavity that occurs during a breath-holding dive under water. During the descent, an increase in pressure causes air spaces and gas pockets within the body to compress." credited : Britannica

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Physics high school-fluid

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Problem# h2phy2 - Pressure on the floor
Problem# h2phy1 - Blood Pressure inside the Aorta

The average gauge pressure in the human aorta is about 100 mmHg.
Convert this average blood pressure to pascals.

Strategy - the rule "Must have" of Mr.Zhang ® memorized (1)Atmospheric pressure,(2)Gauge pressure,(3)Absolute pressure.

Atmospheric pressure (Pa)

Barometer is a measurement tool for measuring air pressure. Barometers measure the current air pressure at a particular location in "inches of mercury" or in "millibars" (mb).

How much pressure are you under? Earth's atmosphere is pressing against each square inch of you with a force of 1 kilogram per square centimeter (14.7 pounds per square inch).

1 atm is calculated by formulae pHggh    →  pHg=13.6x10 3 kg/m3 Therefore, 13.6x103 kg/m3x9.8 m/s2x0.76 m.=1.01325x105Nm-2 =1.01325x105Pa = 1 atm

1 atm = 760 mmHg = 760 torr = 29.9 in.Hg =101.325 kPa = 14.7 lb/in.2

Gauge pressure (Pg) is the pressure according to the liquid substance only,at the height level point "h", and it can be calculated by the liquid weight. We calculate the gauge pressure with pgh

Absolute pressure (P) The difference between absolute pressure and atmospheric pressure is called gauge pressure.

P =  (Pg) + (Pa)

Absolute pressure - Atmospheric pressure = Gauge pressure

Solution

Ans.   The average blood pressure is converted to 13.3 kPa

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