42 terms

Chapter 8: Fluid Mechanics

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Fluid Mechanics
The study of how fluids flow and how forces and energy are transmitted through fluids.
Fluid
Anything that flows and takes the shape of its container. (Liquids and Gases)
*When you drive into mountains or on planes your ears pop because the higher you go the thinner the air is therefore the lower pressure outside your body wants inside.
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Pressure
The net force acting perpendicular to the surface and the area over which it acts.
P=F/A
Formula for pressure.
F is
Force in newtons
A is
Area over which the force is applied in square meters
Solid objects only exert pressure in one direction.
Liquids and gases exert pressure equally in all directions.
Fluid Pressure
The fact that liquids and gases exert pressure equally in all directions.
Pascals (Pa)
What is the SI unit for pressure?
Fluid Density
Another factor that determines fluid pressure. When particles are closer together the weight they exert is greater.
Barometer
An instrument used for measuring atmospheric pressure.
Altimeter
An aneroid barometer calibrated for altitude.
Aneroid Barometer
A small portable instrument that measures atmospheric pressure.
Archimedes Principle
The relationship between buoyancy, displaced liquid.
States that an immersed body is buoyed up by a force equal to the weight of the fluid it displaced.

An object surrounded by air buoyed up by a force equal to the weight of the air displaced.
Buoyant Force
When an object is placed in a fluid, it displaces or pushes out of the way some of the fluid. This displaced fluid pushes back on the object.

All objects in a fluid experience a buoyant force. But sometimes the force is not strong enough to lift the object.
The density of water:
1 g/cm³
The density of mercury:
13.6 g/cm³
What is the densest substance on earth?
Iridium
Formula for weight density
Weight/Volume
Pascal's Principle
A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to all points in the fluid.
This applies to all fluids, whether gases or liquids.
How do fluids move in areas of pressure?
Fluids move from areas of high pressure to low pressure.
Daniel Bernoulli
An 18th-century Swiss scientist studied fluid flow in pipes.
Bernoulli's Principle
Where the speed of a fluid increases, internal pressure in the fluid decreases.

The pressure in a moving stream of fluid is less than the surrounding fluid- faster fluid moves less pressure exerted.

More speed and kinetic energy means less internal pressure, and more internal pressure means less speed and kinetic energy.
Boyle's Law
The density of air inside is greater than the density of air outside.
Twice as many molecules in a volume equals double the air density.
If it molecules move at the same speed or have the same temperature the number of collisions will double (pressure is doubled)
An example of a buoyant force
When the boulder is submerged (to be under water) the water exerts an upward force on it - opposite indirection to gravity.
How does gas expand?
It fills all space available to it and exerts pressure.
Streamlines
The smooth paths of bits of fluid. The lines are closer together narrower regions, where the flow speed is greater.
Eddies
A flow that may become chaotic and follow change and curling paths.
Density
Lightness or heaviness of materials of the same size.
It's a measure of how much mass occupies a given space
What is the formula for density?
Mass/Volume
g/mL
What is the SI unit for density?
What happens to pressure as you go deeper into a fluid?
It increases.
How does pressure change as the density of the fluid increases?
It increases.
As the speed of a fluid increase, what happens to pressure?
It decreases.
If the bouyant force on an object is less than its weight, will the object sink of float?
It will sink.
What happens to the volume of a birthday balloon as it rises up in the atmosphere?
It increases.
Whether or not a______________________________.
density and the density of the fluid it is immersed in.
Objects denser than water will sink in water. While objects less dense than water will _______.
float
An object that neither sinks nor floats is called
Neutral buoyancy
The _____ an object is, the more water it will displace.
denser
Pressure in water increases as you dive deeper in a body of water. This is because of _________.
Gravity, it creates this pressure and it is an essential part to buoyant force. It is not possible to create a buoyant force without gravity.
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