Section 3Behavior of Fluids

Section 3Behavior of Fluids

I. PressureI. Pressure

Why the tyre of bike, the airbed and basket ball can be firm to work?

The firmness is the result of The firmness is the result of ___________________________.___________________________.

These particles collide with the ___________ and push the surface __________.

When the tyre or ball are flat, what can you do to resume firmness?

______ particles, stronger force.

Pressure =

Pressure is equal to the force exerted on a surface divided by the total area over which the force is exerted.

Unit:

For a given area, pressure ________ as force increases.

For a given force, pressure _________ as area decreases.

Compare the pressure of A and B applied on the desk.

AB

cube weight

area

A 200 N 25cm2

B 600 N 100cm2

(Don’t think heavier object always exert more pressure!)

II. Atmospheric II. Atmospheric PressurePressure

The atmosphere is the

We live at the bottom of the “air sea”.

1. Atmospheric 1. Atmospheric PressurePressure

Seawater exert pressure on diver

The air around also press force on you.

101.3 kPa = _________ Pa = _________N/m2

__________________ is the pressure of air.• At sea level, atmospheric pressure is ________

So the force on 1 m2 is 101300 N which is about the weight of the truck!

You don’t notice but you take advantage of air pressure.

cleaner

drink from a straw

2. Balanced Pressure2. Balanced Pressure

The force exerted on the desk is about the weight of the truck!

The desk isn’t be crushed because _________________________________________________

With air inside, the iron pail will not be crushed.

Without air, the iron pail will be crushed.

Atmosphere exerts a pressure on all surface of our body.

____________ in your body exert a pressure that balance the atmosphere pressure.

3. Variations in 3. Variations in Atmospheric Atmospheric PressurePressure

In 17th century, French physician Pascal had a experiment.

A balloon partially filled with air expanded while being carried up the mountain.

____________________________________________________________

As altitude increases, the number of air particles ________, so the atmosphere exert _____pressure on the balloon.

4. Air Travel4. Air Travel

Travel to higher altitudes, you might feel a popping sensation in your ears.

To ________air, your ear is heard as a pop.

III. Changes in Gas III. Changes in Gas PressurePressureThe pressure of a gas in a closed container

changes with ________ and ___________.

________volume, more pressure.

The particles have

__________ to move,

so they collide _____

_______ and produce

________pressure.

The particles have ______ kinetic energy to move, so they collide ___________ and thereby produce a ________ pressure.

________ temperature, more pressure

IV. Float or SinkIV. Float or Sink

Water pressure _________ as you swim deeper in water.

Atmospheric pressure __________ as you walk down a mountain.

________ force________ force

________force________force

The difference in pressure results in an upward force—— _________________

Archimedes’ Archimedes’ PrinciplePrinciple

The buoyant force on an object is equal to __________________________________________________________________.

The buoyant force on object =

Buoyant force

weight

Buoyant force= weight, _________Buoyant force < weight, __________Buoyant force > weight, __________________

Density=

A tourist is floating on Dead Sea.

The Dead Sea dissolved __________ so The Dead Sea dissolved __________ so that its density is ______than the that its density is ______than the man’s density.man’s density.

Why an iceberg can float on water?

Because ______________

____________________

________________.

For most matter, Dsolid > Dliquid

But _____ is exception!

How to make a balloon float in air?

(1)

(2)

Why the steel ship can float on water even the density of steel is much greater than water?

Archimedes' Principle explains why steel ships float.               

_________________________________________________________________________________________________________________.

Example:

A 4.60 cm3 sample of a solid has a mass of 10.0g. Will it float in water? (density of water is 1.00g/cm3)

V. Pascal’s V. Pascal’s PrinciplePrincipleWhen a force is applied to a confined

fluid,

___________________________________________

_________________________.

force force

water

The pressure increases equally everywhere

Application of Pascal’s Principle

Hydraulic system use Pascal’s principle to ____________, which enable up to lift heavy objects using __________________.

Force= pressure ×area

Downward force=500 N

Upward force=10,000 N

Ex: A hydraulic device has two pistons. How much force do you have to apply to the piston with an area of 10 cm2 to lift an object weighting 2,000 N on a piston with an area of 50 cm2?

? N? N10 cm10 cm22 2000 N2000 N

50 cm50 cm22

Force pumpForce pumpFluid in a closed container which has a hole will __________________________________________________________.

In heart, ______________ work together to move blood to and from the lungs and to the rest of the body.

Blood from the body

Blood to lungs

Blood from lungs

Blood to body

1. Which change results in an increase in gas pressure in a sealed, flexible container?

A) Decrease in temperature.B) Decrease in volume.C) Increase in volume. D) Increase in altitude.

2. Which is a unit of pressure?A) N B) kg C) g/cm3 D) N/m2

Learning CheckLearning Check

3. In which case will an object float on a fluid?

A) Buoyant force is greater than weight.B) Buoyant force is less than weight.C) Buoyant force equals weight. D) Buoyant force equals zero.

4. Which is equal to the buoyant force on an object?

A) Volume of the objectB) Weight of the displaced fluidC) Weight of objectD) Volume of fluid

A king’s crown has a volume of 110 cm3 and a mass of 1800 g. The density of gold is 19.3 g/cm3. Is the crown pure gold?

CalculationCalculation