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# Grade 8 Mix and Flow of Matter - Fluid Pressure

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## Nairn McLean

on 2 February 2015

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#### Transcript of Grade 8 Mix and Flow of Matter - Fluid Pressure

Pressure in Fluids
Pressure
the force acting perpendicular to certain surface area
Particle Theory
particles are solids, liquids, and gases that are constantly moving.

- collisions between individual particles create
Compressibility
Solids and liquids are called
Incompressible
because the spaces between the particles are not large enough to be compressed;
instead of changing volume, the applied force is
transmitted
(passed along)from one particle to the next.
Expanding!
Under pressure gases are ready to expand again, because the particles have so much energy.
if gases under pressure find a way to escape from a container - with great force.
Depth and Temperature
Pressure in Depth
Particle Theory of Matter
a scientific model of the structure of matter
one part of this theory states that all matter is made up of extremely small particles
Under Pressure
Queen
"Pushing down on me, pushing down on you."
PRESSURE
Solid State:
- particles have the least amount of energy
- strong bonds prevent particles from moving freely
- particles are packed together so tightly that solids
Liquid State:
-the bonds are broken so particles can move and slide past each other.
- Liquids flow and but particles are still packed closely so
Gas State:
- liquid becomes gas by heating it strongly.
- when particles have enough energy they can break free from the weak bonds
- the particles move rapidly in all directions
we experience pressure in fluids everyday.
Flow pressure
: causes motion because the fluid is moving, therefore, water running out of faucet.
Static pressure
: fluid pressure exerted by a force on an object even if the fluid is moving. For example, in a swimming pool
Pressure affected by temperature
Experiment! in cold and hot conditions
Formula for Pressure*
Pascal Law: named after the French scientist Blaine Pascal (1623 - 1662) states that when pressure is exerted on one part of the fluid, the same pressure is transmitted unchanged to all parts of the fluid, no matter what the shape of the container holding the fluid.
pascal (Pa) a unit for pressure; newtons per square metre (N/m2)
* In case
Hydraulics
- the study of pressure in liquids.
Hydraulic system
- a device that transmits an applied force through a liquid to move something else by means of pressure
Ex. Jaws of Life
Fluid Movement
- liquids under pressure flow away from the applied force.

- The pressure need to be enough to transport fluid but not enough to burst pipe
Pump Stations
- are needed to restore the pressure lost on long routes and maintain a water supply to your house.

- to regulate the flow of liquids, we use the devices of
valves.
Body Hydraulics
- blood must be kept under pressure so it can reach all parts of the body
- Blood pressure: the pressure of the blood in the circulatory system. The heart is the pump
Air Pressure Pneumatic System
- Pneumatics, the study of pressure in gases
- Pneumatic system: a system in which a gas, transmits a force exerted on the gas in an enclosed space
- Air pressure changes with altitude; this explains why our ears pop
Barometer
, is a common device used in measuring air pressure made with mercury. Used in weather stations.
Aneroid barometer
are used at home and contain no liquids.
The Pneumatic System
- its based on the fact that gases can be compressed.
- Compressors (devices that compress air) and pressure is released when the air is decompressed. For example, trucks and buses use pneumatic brakes to stop quickly and smoothly
- the property of gases is also their ability to exert a force back when they are compressed and used to cushion shocks. For example, the air in a tire. So if a car hits a bump, the extra force compresses the air in the tires even farther.
Sphygmomanometer is blood
pressure monitor used to measure
the pressure exerted by the blood
pushing on the walls of an artery
Vacuum - a space in which there is little air. Therefore, no pressure
*8:20 - 10:08 minutes
The ability to be squeezed into a smaller volume,
a property of gases.
What part of the particle model would help explain how gases are able to be compressed?

Solids
Cannot
be compressed.
Liquids
cannot
be compressed.
Gases
CAN
be compressed
Gases are what is called
compressible
because there is space between the particles, and in a gas particles are extremely far apart, the gas can be compressed
EXAMPLE 1:
Find the pressure when a 200N force is applied to a 0.5m area?
2
P = F/A
P = 200N / 0.50m

= 400N/m
= 400Pa
2
EXAMPLE 2:
P = ?
F = 200N
A = 0.50m
2
Calculate the area where a 300N force was applied resulting in 35Pa of pressure?
P = F/A
P = 35Pa
F = 300N
A = ?
P
F
A
A = F/P
A = 300N / 35Pa
= 8.75m
2
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