1. Notes – Pressure & Buoyant Force
Chapter 3, Lesson 2

2. Pressure in a Fluid
A fluid is a material that can flow and has no definite shape.
Liquids and gases are fluids.
Fluids can exert forces.

3. Pressure in a Fluid
Pressure is the force per unit of area applied on the surface of an object.
Pressure depends on the area over which a force is exerted.
If the area increases, pressure decreases.

4. Pressure in a Fluid Pressure depends on the size of the force.
If the force increases, pressure increases.

5. Pressure in a Fluid The equation for pressure is: P = F ÷ A
Pressure (pascals) = force (newtons)
area (meters squared)
The SI unit of pressure is the pascal, abbreviated Pa. A pressure of 1 Pa is equal to a force of 1 N applied over an area of 1 m2
1 Pa = 1 N / m2

6. Pressure in a Fluid
For any liquid in a container of any shape, the pressure depends only on the height of the column of liquid above the surface where you measure the pressure.

7. Pressure in a Fluid
The deeper underwater you go, the greater the pressure is on you. This is because as you go deeper, the column of water above you gets taller.

8. Pressure in a Fluid
In a fluid, pressure is exerted on all points on the outside of an object in a direction perpendicular to the surface of the object at that point.

9. Pressure in a Fluid
A gas, like any fluid, exerts a pressure on an object. That pressure depends on the height of the gas above the object.

10. Pressure in a Fluid
Atmospheric pressure is the force exerted per unit area by air particles.
As you climb, or increase your elevation, atmospheric pressure decreases.

11. Pressure in a Fluid
Atmospheric pressure at sea level is caused by a large weight of gas, but is difficult to notice because there is an equal, internal pressure pushing out from the inside of your body.

12. Buoyant Force
The buoyant force is the net upward force exerted on an object in a fluid by the surrounding fluid. It acts against gravity.

13. Buoyant Force
In a fluid, there is no net horizontal force on an object caused by pressure from the fluid.

14. Buoyant Force
Because in a fluid, pressure increases with depth, the force of the fluid pushing up on the bottom of an object is always greater than the force of the fluid pushing down on the top of the same object.

15. Buoyant Force
The size of the buoyant force does not depend on depth.

16. Buoyant Force
Archimedes’ Principle states that the buoyant force on an object is equal to the weight of the fluid the object displaces.

17. Pressure is the ____ per unit area. A mass B volume C force D pascal
3.2 Pressure and the Buoyant Forces
Pressure is the ____ per unit area.
A mass
B volume
C force
D pascal

18. Which direction does the buoyancy force act on an object? A upward
3.2 Pressure and the Buoyant Forces
Which direction does the buoyancy force act on an object?
A upward
B downward
C to the left of the object
D to the right of the object

19. Where is the pressure the greatest on an object in a fluid? A top
3.2 Pressure and the Buoyant Forces
Where is the pressure the greatest on an object in a fluid?
A top
B bottom
C sides
D none of the above

20. Vocab – Pressure & Buoyant Force
TB p
force
fluid
pressure
atmospheric pressure
buoyant force
Archimedes’ principle