1. Fluids Objectives: Pressure inside fluids Hydraulic Lift
Buoyancy Force and Displaced Volume
Bernoulli’s Principle

2. Pressure inside fluids
(density) (g) (height) =
Pressure
Pressure depends ONLY on the depth (height of fluid on top)
height
Q1. How much is the pressure inside the pool, 1 m below the water surface?

3. How do we measure pressure?
Units:
Pressure on RIGHT side is greater
“Water seeks its own level” when the pressure on both sides is equal
Pressure on LEFT side is greater

4. How do we measure pressure?
Q2. Which pressure is higher?
(a) Gas
(b) Atmospheric Pressure
(c) Both are the same
(a) Gas
(b) Atmospheric Pressure
(c) Both are the same

5. Hydrostatic Pressure 20
P1. While standing, your blood pressure is normally greatest in your
(a) head
(b) heart
(c) feet
(c) same in each
P2. The pressure in a liquid depends on liquid
(a) density
(b) depth
(c) Both of these
(d) Neither
P3. What is the mass of 1 cubic meter of water?
Ans.
P4. Lobsters live on the bottom of the ocean, which means their density is
(a) Greater than the density of sea water
(b) Equal to the density of sea water
(c) Less than the density of sea water

6. The Hydraulic Lift Pascal’s Principle:
Force (out) =
Area (out)
Force (in)
Area (in)
Q3. You apply a force of 100 N on a piston with an area of 1.0 cm2. What can you lift on the other side where the area of the platform is 4.0 m2?

7. The Hydraulic Lift 20
P1. You apply a force of 100 N on a piston with an area of 1.0 in2. What force does the fluid exert on the other side where the area of the platform is 25 ft2
Ans.
P2. In a hydraulic system a 20.0-N force is applied to the small piston with cross-sectional area of 25.0 cm2. An object with what mass can be lifted by the large piston with area 50.0 cm2.
Ans.
P3*. Compressed air in a car lift applied a force to a piston with radius 5.00 cm. This pressure is transmitted through a hydraulic system to a second piston with radius 15.0 cm. How much force must the compressed air exert to lift a vehicle weighing 1.33 x 104 N?
Ans.

8. Displaced Volume
An object submerged in fluid displaces volume that is equal to its own volume
Example: A 784-g object
Displaces water as shown:
Object is submerged
Water Level is now:
190 mL
Initial Water Level:
150 mL
Note:
1 mL is the same as
1 cm3 ( the same as cc)
Find the Volume of the object
Find the density of the object
Volume of the object is : 190 mL – 150 mL = 40 mL = 40 cc (cubic centimeters)
Density: (784 g) / (40 cc) = 19.6 g/cm3

9. Bernoulli’s Principle
Increase in speed occurs simultaneously with decrease in the pressure for a fluid flowing horizontally.
Examples
Airplane Wing: Wings are designed
So that air above them moves faster
Than the air below the wing.
The pressure at the bottom is then
Larger than the pressure on top –
Lift Force
Cars at intersection: As you wait for a left turn, whenever
A car that goes straight passes you, you feel a pull towards
The car