# 8fluid1 - Fluids Density Density is defined as mass per...

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1 Density Density is defined as mass per unit volume. Fluids 1 Specific Gravity (SG) = Density / Density of water at 4 o C Density Density is defined as mass per unit volume. 2 Solids Magnesium 1.7 Aluminum 2.7 Copper 8.3-9.0 Gold 19.3 Iron 7.8 Lead 11.3 Platinum 21.4 Uranium 18.7 Material Density (gm/cm 3 ) Liquids Water at 4 C 1.0000 Water at 20 C 0.998 Gasoline 0.70 Mercury 13.6 Milk 1.03 3 The density in kilograms per cubic meter can be obtained by multiplying the table values by 1000. Osmium 22.5 Ice at 0 C 0.92 Gases at STP Air 0.001293 Carbon dioxide .001977 Carbon monoxide 0.00125 Hydrogen 0.00009 Helium 0.000178 Nitrogen 0.001251 Pressure 4

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2 Pressure 5 At Sea level: 1 atm = 101325 Pa 1.013×10 5 Pa = 760 mmHg = 760 Torr Atmospheric Pressure (atm) 6 At some heights above the earth are: Height Measured Predicted pressure pressure 30 km (19 mi) 9.5 torr 25 torr 60 km (37 mi) 0.21 torr .8 torr 90 km (56 mi) 0.0019 torr .03 torr Pressure Equation • The pressure on a surface is the perpendicular force per unit area acting on the surface. • Pressure is force per unit area: • units: Newton/(meter) 2 =Pascal (Pa) – pressure exerted by the weight of a dollar bill is about 1 A F p = 7 Pa – 1 atmosphere is about 1.103 5 Pa • direction: always perpendicular to surface Example: Pressure is force per unit area. A force of 150 N applied to a piston of area 0.001 m 2 in a tire pump results in a pressure of 1.5 x 10 5 N/m2 = 1.5 x 10 5 Pa. 8
3 Example: What is the pressure on the base of the bathtub? The volume of water is = (length) (width) (height) = l*h*w =0.234 m 3 The weight = volume *density * gravity = 2293.2 N Force (F) = weight = 2293.2 N Pressure (P) = weight / area = 2940 N/m 2 9 Examples 1. The contraction of the left ventricle (chamber) of the heart pumps blood to the body. Assuming that the inner surface of the left ventricle has an area of 79 cm2 and the maximum pressure in the blood is 125 mm-Hg, estimate the force exerted by the ventricle at maximum pressure. 2. During each heartbeat, approximately 68 cm 3 of blood is pushed from the heart at an average pressure of 105 mm-Hg. Calculate the power output of the heart, in watts, assuming 76 beats per minute. 3. You want to build a vacuum vessel that is a cube 20 cm on a side. How much force does each side have to withstand? 10 p=0 p=1 atm Static Fluid Pressure The pressure exerted by a static fluid depends only upon the depth of the fluid, the density of the fluid, and the acceleration of gravity. P

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8fluid1 - Fluids Density Density is defined as mass per...

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