2. Measured in Newtons per metre squared (N/m2) or Pascals (Pa)
Pressure and surfaces.
Pressure and surfaces
Pressure = Force/Area
Measured in Newtons per metre squared (N/m2) or Pascals (Pa)
“The larger the area a given for is acted on, the smaller the pressure will be”
What is pressure?

3. Pressure in liquids? 1) The particles move quickly in all directions.
2) Eventually they bump into each other or the walls of their container. When particles hit the walls of their container they exert a force, this causes pressure
3) The more particles that hit the walls, the higher the pressure.

4. Pressure in liquids Pressure in a liquid: acts in all directions;
increases with depth.
A liquid can be used to transmit pressure from one place to another.

5. How can we calculate the pressure at different depths?
Pressure = gravitational field strength x density of liquid x height of water “above” (ie depth)
P = gρh

6. P = gρh Atmospheric Pressure
Air pressure is due to gas molecules colliding.
At higher altitudes, air is less dense
Fewer molecules per cubic meter
Fewer collisions
Lower pressure
P = gρh
Limitations of this equation?
Density of air isn’t constant.
At VERY large heights, g isn’t constant.

7. Pressure greater here…..
Upthrust
Submerging objects into water they will displace a volume of water.
There is a resultant force acting on the object pushing it upwards.
This is upthrust.
Than here…..
Submerged objects experience an upthrust equal to the weight of water which has been displaced.
Pressure greater here…..
If upthrust = weight of object
If upthrust < weight of object
FLOAT
SINK