Pressure in Fluids
• Pressure depends on force and area.
• If you spread the force over more
area, there is less pressure.
Which creates more pressure?
10 cm
10 cm
20 N Push
5 cm
5 cm
20 N Push
If this woman were to step on you, which
part of the shoe creates more pressure?
Force
(weight)
Force
(weight)
Area
Same force
over smaller
area creates
more pressure
under the heel.
Pressure in Fluids
• Pressure depends on force and area.
• If you spread the force over more
area, there is less pressure.
• The formula to calculate pressure is:
Pressure =
force
area
The S.I. unit that we use for pressure is the pascal (Pa)
What causes fluid pressure?
• Pressure in fluids is caused by the
particles pushing against a surface.
• Each particle gives a teeny tiny push,
but they all add up.
• The more crowded the particles are, the
harder they push.
• The faster they are moving, the harder
they push.
Less Fluid
Lower Pressure
More
Fluid
Higher Pressure
Is
Because air has weight,
and if there is less air above you,
there then
lessthere
pressure
more
pressure
will be or
less
weight.
Why?
the causes
mountain?
The weightonoftop
theoffluid
the pressure!
Plastic bottle sealed at 14,000 feet on Mauna Kea
observatory on the island of Hawaii, taken down to 9000 feet
and then 1000 where the air pressure is crushing the bottle.
You can’t feel
If the
air has
weight, why
atmospheric
pressure
your
don’t because
we feel the
body
fluids push
back!
atmospheric
pressure?
The forces are balanced.
Less Fluid
More
Fluid
Because water has weight,
and if there is more water above you,
Is
there
more
pressure
then there will be more weight.
How
you
on the do
divers
or theknow?
shark?
The weight of the fluid causes the pressure!
What part of an iceberg has the
most pressure on it?
Pressure
increases
as you
get
deeper!
Remember
that pressure
pushes in
all directions
so the
iceberg is
being pushed
on all sides,
all the way
around.