1 2/10/2004 ISP 209 -- 5A 1 Fluids Fluids i.e., gases and liquids i.e., gases and liquids 2/10/2004 ISP 209 -- 5A 2 A fluid is a material that can flow. Liquids Liquids - water in a river - molten iron in a steel plant Gases Gases - steam in a heating pipe - air on a windy day The opposite of a fluid is a solid.
12
Embed
Fluids i.e., gases and liquids - Michigan State University · PDF filei.e., gases and liquids 2/10/2004 ISP 209 -- 5A 2 A fluid is a material that can flow. Liquids ... Flowrequires
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
2/10/2004 ISP 209 -- 5A 1
FluidsFluids
i.e., gases and liquidsi.e., gases and liquids
2/10/2004 ISP 209 -- 5A 2
A fluid is a material that can flow.
LiquidsLiquids- water in a river- molten iron in a steel plant
GasesGases- steam in a heating pipe- air on a windy day
The opposite of a fluid is a solid.
2
2/10/2004 ISP 209 -- 5A 3
Flow requires the ability to change shape.
In a gas or liquid, the molecules are free to slide around – not held at fixed positions.
In a solid, the molecules are held in fixed relative positions.
2/10/2004 ISP 209 -- 5A 4
Two familiar examples of fluidsWater . . . hydrodynamicsAir . . . aerodynamics
3
2/10/2004 ISP 209 -- 5A 5
Two important parameters of any fluid are• density ρ = mass per unit volume [kg/m3]• pressure p = force per unit area on a surface in contact with the fluid [N/m2 = Pa for pascal]
Useful numbers for the CAPA
ρ (water) = 1.00 x 103 kg/m3
p (air at STP) = 1 atm = 1.013 x 105 Pa = 14.7 psi
Density and PressureDensity and Pressure
2/10/2004 ISP 209 -- 5A 6
Buoyancy
Why do hot air balloons go up?
How can a great battleship float in water?
Archimedes’ Principle
4
2/10/2004 ISP 209 -- 5A 7
ArchimedesArchimedes
This greatest scientist and mathematician of ancient Greece made many discoveries:
• accurate value of π
• volume and area of a sphere
• levers and machines: “Give me a lever long enough and a place to stand and I will move the Earth.”
• density and buoyancy: The story of the King’s crown
The story of his death
2334 4 rr ππ and
71
7110 33 +<<+ π
his book On Floating Bodies
2/10/2004 ISP 209 -- 5A 8
Archimedes lived in the Greek kingdom of Syracuse on the island of Sicily. The Roman army and navy laid siege to Syracuse. Archimedes, an old man at the time, was put in charge of the defense of the city. He held off the Romans for about a year with military inventions like the Claw.
Archimedes’ Claw
5
2/10/2004 ISP 209 -- 5A 9
Archimedes screw pump
Where have you seen this, and what is it?Where have you seen this, and what is it?
2/10/2004 ISP 209 -- 5A 10
Archimedes’ Principle of Buoyancy
An object immersed in a fluid experiences an upward force equal in strength to the weight of the displaced fluid.
This force is called the buoyancy force.
6
2/10/2004 ISP 209 -- 5A 11
Why?Imagine the object replaced by a fluid element of the same shape.
Weight of the fluid element
Buoyancy forceIn static equilibrium the buoyancy force must balance the weight of the equivalent fluid element.
The buoyancy force on the original object is the same as the buoyancy force on the equivalent fluid element.
Q. E. D.
2/10/2004 ISP 209 -- 5A 12
Floating or sinking?
gVFgVMgF
×=
×−=−=
fluidbuoyancy
objectgravity
ρρ
gravity, weight
buoyancy Suppose an object of mass M and volume V is completely immersed in a fluid. Will it rise or sink?