Chapter5 Solidandliquidbb101 121014064519 Phpapp02

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Boardworks Ltd 20041 of 20


Chapter 5

Solids & Fluid


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Solids, Liquids and Gases

Pressure

Characteristics of Solid, Liquid and Gas

Density and relative density

Contents

Pascal Principle

Archimedes Principle


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Three states of matter

solid liquid gas

At room temperature most substances exist in one of three

physical states.


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The particle model

The difference between solids, liquids and gases can be

explained by the

All substances are made up of particles.

The particles are attracted to each other. Some particles

are attracted strongly to each other and others weakly.

The particles move around. They are described ashaving kinetic energy.

The kinetic energy of the particles increases withtemperature.
http://h/power%20point%20azah/States%20of%20Matter.rvhttp://h/power%20point%20azah/States%20of%20Matter.rv


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Particles in a solid


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Particles in a liquid


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Particles in a gas


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click
http://h/power%20point%20azah/States%20of%20Matter.rv


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Properties of solids, liquids and gases


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How do smells spread out?

Where is the smell coming from and how does it spread out?



Diffusion occurs in liquids and gases but hardly at all in

solids.

What is diffusion?

Diffusion is themovement of

particles that allows them to spread

out and mix with other particles.

For example, the smell of aftershave

or perfume diffuses and is detected by

people on the other side of the room.

Use the particle model to explain these facts about diffusion:

Diffusion happens more quickly for gases than for liquids.

Diffusion happens more quickly at warm temperatures

than at cooler temperatures.



Across:

2. Change from liquid to solid

5. Force caused by collisions ofparticles

6. Arranged in a 3-dimensional

pattern

9. Spacing of particles in solidsand liquids

10. All substances are this state

at very low temperatures

11.Only liquids and gases do this

1

2 3

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6

7 8

9

10

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Down:1. Closely packed particles 6. Particles are close but disorganised

3. Change from gas to liquid 7. Particles widely spread out

4. Change from solid to liquid 8. Change from liquid to gas

Crossword



DEFINE DENSITY,

Density is defined as ratio of the mass of substance to its

volume. It is a measure of how tightly packed and how heavy the

molecules are in an object. Density is the amount of matter within a

certain volume.

Proof that water and ice have

different densities



To find the density

Find the mass of theobject

Find the volume of

the object

DEFINE DENSITY

Units for density usually express

in kg/m3

= m (kg)

V (m3)



Example 1:

A big box has mass of 20N and size 30cmx30cmx30cm,

Using all the information, calculate the density of the box.

Solution:

W = mg

20 N = m (9.81)

m = 20 / 9.81

= 2.04 kg

Volume = 30cm x 30cm x 30cm

= 0.3m x 0.3m x 0.3m

= 0.027m3

30cm

30cm

30cm

= m = 2.04 kg = 75.57 kg/m3

V 0.027m3



Also known as Specific Gravity Specific gravity is ratio of the density of a sunstance to the

density t of water.

DEFINE RELATIVE DENSITY, b

b= substance (kg/m3)

water (kg/m3)No unit

1000 kg/m3

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Example 2:

If the density of an object is 4000 kg/m3 ,calculate the

specific gravity of the object. ( Density of water = 1000 kg/m3)

b= subs tance (kg/m3)

water (kg/m3)

b= 4000(kg/m3)1000(kg/m3)

= 4

PRESSURE P



PRESSURE, P

Pressure is defined as Force per unit Area acting on a surface.

Factors that affect the pressure acting on a surfaceContact area ( Smaller contact area greater pressure)

Force acting on the surface ( Large force greater pressure)

P = F (N)

A (m2)

Unit in N/m2 or Pascal (Pa)

A

F

A

F

APPLICATION OF PRESSURE



APPLICATION OF PRESSURE

High Pressure Low Pressure

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Example 3:

How many Pascals are exerted by an elephant of weight

50 000 N standing on his feet of total area 0.8m

2 ?

Solution:

F = 50000 N

Area = 0.8m2

P = F / A

= 50000 / 0.8

= 62 500 Pa

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Example 4:

What Pressure is exerted by an apple of weight 1 N sitting

on area 20mm

2

?Solution:

F = 1 N

Area =20 mm2 = 0.00002m2

P = F / A

= 1 / 0.00002

= 50 000 Pa

PRESSURE IN LIQUID



PRESSURE IN LIQUID

A liquid in a container exerts pressure because of it weight (Force).

P = gh Unit in N/m2 or Pascal (Pa)

A

h

Volume, V = Ah

Density, = mV

Mass, m = V

Weight,w = Force,F = mg= Vg

= Ahg

Pressure = F = Ahg = hgA A

CHARACTERISTICS OF PRESSURE IN A LIQUID




Depth to pressure in liquid

Liquid pressure increase

with depth

The pressure of water isthe lowest at the highest

point of the cylinder and

the pressure of water is

highest at the lowestpoint of the cylinder.



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Density to pressure in liquid

Pressure of liquid is increases with density.

Water Oil

x1 x2

x1 > x2 Density of cooking oil is less than water



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Fluid exerts forces in many directions. Try to submerse a

rubber ball in water to see that an upward force acts on thefloat.

Fluids exert pressure in

all directions.F




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Water seeks its own

level, indicating that

fluid pressure is

independent of area

and shape of itscontainer.

At any depth h below

the surface of the

water in any column,the pressure P is the

same. The shape and

area are not factors.

h

Water

level

Independence of Shape and Area

Example 5:


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Example 5:

The figure shows a cross section of a dam. Calculate;

a.The pressure exerted by the water at X, if the density of

water is 1000kg/m2

b.Explain why the bottom of the dam is built with thick

wall?

c.If there is air exerted and given that Patmis 101.3Kpa.

What is absolute pressure at point x?

6.5mx0.5m


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Solution:

a) Px= watergh

= (1000)(9.81)(6.5-0.5)

= 580860 Pa

b) This is because the water pressure increase as the

depth of water increases. So, a grater pressure is

exerted at the bottom of the dam.

c) Pabsolute = Patm + Px

= 101.3 kPa + 580860 Pa

= 682.16 kPa

APPLICATION OF PRESSURE IN LIQUIDS


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APPLICATION OF PRESSURE IN LIQUIDS

Public water supply

systems ( Water Tank)

The wall of a dam

PASCAL PRINCIPLE


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PASCAL PRINCIPLE

Pascals principle states that pressure exerted on an

enclosed fluid is transmitted equally to every part of the

fluid.

P1 = P2

F1= F2

A1 A2

Pressure in Pascal can be

expressed:

A1d1= A2d2

Transmitting force


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Transmitting force

An applied force F1can beamplified:

Hydraulic press

P F1

A1

F2

A2

F2

F1

A2

A1

A common application of this is a hydraulic lift used to raise

a car off the ground so it can be repaired at a garage.

Example


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Example

The cylindrical piston of a hydraulic jack has a cross-sectional

area of 0.06 m2 and the plunger has a cross-sectional area of

0.002m2.a.The upward force for lifting a load placed on top of the large

piston is 9 000 N. calculate the downward force on the

plunger required

b.If the distance moved by the plunger is 75cm, what is the

distance moved by the large piston?


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Solution:

a) F1 = F2

A1 A2

F1 = F2A1

A2

= 0.002 x 9 000

0.06

= 300 N

b) A1d1 = A2d2

d2 = A1d1

A2

= 0.002 x 75

0.06

= 2.5cm

APPLICATION OF PASCAL PRINCIPLE


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APPLICATION OF PASCAL PRINCIPLE

Hydraulic Brake Hydraulic Jack

ARCHIMEDES PRINCIPLE


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Archimedes' principle is the law of buoyancy.

It states that "Any object partially or completelysubmerged in a fluid is buoyed up by a force equal to the

weight of the fluid displaced by the body."



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Buoyant force = Weight of fluid displaced

Buoyant force = Weight object in airweight in water

Buoyant force = Vg


Volume of the submerged = Volume of the liquid

object displaced



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Related buoyant force with the actual weight and

apparent weight


Buoyant force makes things

seem to be lighter.

The weight of an object is its

actual weight.

The weight measured whenthe object is immersed in fluid is

its apparent weight.

The apparent weight loss of

the object is due to buoyantforce

Buoyant force = Apparent

weight Loss

Law of Floatation


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Law of Floatation

A floating object displaces its own weight of fluid in

which it floats.

Buoyancy explains why some objects sink and othersfloat.

Objects that are less density than water will float.

Objects that are more density than water will sink.

Objects that are the same density as water will neither

sink nor float.

Law of Floatation


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Law of Floatation

Which ball will sink in water?Which ball will float in water?

APPLICATION OF ARCHIMEDES PRINCIPLE


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APPLICATION OF ARCHIMEDES PRINCIPLE

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