1. Pressure in Fluids Pressure depends on force and area.
If you spread the force over more area, there is less pressure.

2. Which creates more pressure?
10 cm
20 N Push
10 cm
5 cm
20 N Push
5 cm

3. Same force over smaller area creates more pressure under the heel.
If this woman were to step on you, which part of the shoe creates more pressure?
Same force over smaller area creates more pressure under the heel.
Force
(weight)
Force
(weight)
Area

4. Pressure in Fluids force Pressure = area
Pressure depends on force and area.
If you spread the force over more area, there is less pressure.
The formula to calculate pressure is:
force
Pressure =
area
The S.I. unit that we use for pressure is the pascal (Pa)

5. 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.

6. The weight of the fluid causes the pressure!
Less Fluid
Lower Pressure
More Fluid
Higher Pressure
Because air has weight,
and if there is less air above you,
then there will be less weight.
The weight of the fluid causes the pressure!
Is there less pressure or more pressure
on top of the mountain?
Why?

7. 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.

8. The forces are balanced.
You can’t feel
the atmospheric
pressure because your
body fluids push back!
The forces are balanced.
If air has weight, why don’t we feel the atmospheric pressure?
Force out
Force in
Force in
Force out
Force out
Force out
Force in
Force in

9. The weight of the fluid causes the pressure!
Less Fluid
More Fluid
Because water has weight,
and if there is more water above you,
then there will be more weight.
The weight of the fluid causes the pressure!
Is there more pressure
on the divers or the shark?
How do you know?

10. What part of an iceberg has the most pressure on it?
Remember
that pressure
pushes in
all directions
so the
iceberg is
being pushed
on all sides,
all the way
around.
Pressure
increases
as you
get
deeper!