What are Some
Characteristic of
Fluid Pressure ?
Day 1
Depth effects pressure
As depth increases, water pressure increases
(directly proportional)
Depth
Pressure
Altitude effects Pressure
As altitude increase, air pressure decreases
(inversely proportional)
Altitude
Pressure
Atmospheric Pressure
• The atmosphere is a fluid: a thin layer of nitrogen,
oxygen, and other gases that surrounds Earth.
• Atmospheric pressure is the pressure caused by
the weight of the atmosphere.
• Atmospheric pressure is exerted
on everything on Earth….
including you!
Are you under a lot of pressure?
Do
you
feel
a
lot
of
pressure?
https://www.youtube.com/watch?v=1nveW
CRiIlo
PRESSURE!
Right now, 1000 kg of air are pushing on the top of
your head!
What is a Force?
• Any push or pull (unit: Newton or N)
• Weight is a Force (W = m x gravity)
What is pressure?
• The result of a force distributed over an area
• Pressure = force = Newton
area meters2
• SI unit of pressure is the pascal (Pa)
• 1 Pa = 1 Newton/1m2
Juice Falls
FLUID
PRESSURE
Day 2
Or feeling a bit stressed lately???
What is pressure?
• The result of a force distributed over an area
• Pressure = force = Newton
area meters2
• SI unit of pressure is the pascal (Pa)
• 1 Pa = 1 Newton/1m2
For example:
Sharp
Knife vs Dull Knife
• Sharp knife exerts a LARGE FORCE over a small
area
• FORCE/ area = PRESSURE
• Dull knife exerts a small force over a LARGE
AREA
• Force/AREA = pressure
You do the math
• Sharp knife: area = 1 mm2
• Dull knife: area = 5 mm2
• Force applied to each knife = 5 N
Sharp knife = 5/1 = 5N/m2
Dull knife = 5/5 = 1N/m2
Another example:
•
•
•
•
Ice skating (or roller blading)
A shoe distributes the force (body weight)
over a much larger area than the skate
So the skate exerts a much higher pressure on
the ice than the shoe does
The skate pushes into the ice and
Voila! You can skate!
Examples
• If the area of a box
touching the ground is
1.5 square meters, and
its weight is 2700
newtons, what pressure
does the box exert on
the ground?
• A gymnast standing on
one hand (area 0.02 m2)
pushes down on the
ground with a force of
600 N. How much
pressure does the
gymnast exert on the
ground?
So . ……..
• The greater the area the
force is distributed over,
the less the pressure
Day 3- Fluids Flow
So What are Fluids?
• A substance that can flow and takes the shape
of it’s container (no definite shape)
• Examples: gases and liquids
• Fluids exert pressure
Fluids want to . . .
• Move from areas of high pressure to areas of
low pressure
• Everything wants to be equal
Pressure Differences and Fluid Flow
Just by drinking through a straw you can observe
an important property of fluids: Fluids flow from
areas of high pressure to areas of low pressure.
Pressure Differences and Tornadoes
The air pressure inside a tornado is very low.
Because the air pressure outside of the tornado is
higher than the pressure inside, air rushes into the
tornado.
The rushing air causes the tornado to be like a giant
vacuum cleaner.
PRESSURE!!!
Can Crusher
Standard atmospheric pressure = 14.7
pounds per square inch (psi)
• What happened to this can?
Everything wants to be equal!
• Pressure on the outside >>>> pressure on the
inside
• So when the can is heated, the can is crushed!
• Why?????