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# PHYSICS

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## EMPERIND

on 28 March 2018

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#### Transcript of PHYSICS

PHYSICS
UNITS & MEASUREMENTS
Measurement

is the quantity to be measured with a reference
standard .
the reference standard of measurement is know as
unit .
They are seven basic units in a number's
length , mass , time , electric current , temperature ,light
intensity , and amount of substance.
The other units which can be derived from basic units are called as derived units .
There are

three

systems of units which are utilized for measurements .

THE CGS SYSTEMS :-
It is based on the three basic units ,
the Centimeter
,
the gram and second for the the length
,
mass and time measurement respectively
THE FPS SYSTEM :-
it is used on the basics of the foot ,pound

and the second for length , mass and time measurement respectively
THE MKS SYSTEM :-
It is based on metre for length the kilogram
for mass and the second for time.
( SI )
:-
SYSTEM INTERNATIONAL UNIT

The seven basic units are globally accepted and utilizers by this unit
Basic unit of measurement
SI Units
length metre ( m )
mass kilogram ( kg )
time second ( s )
temperature kelvin ( k )
electric current ampere ( a )
light intensity candela ( cd )
amount of subtance mole ( mol )

LENGTH :-

is associated with the distance , and defined as the
distance of separation between two points in space.
the unit of length is SI unit is metre.it has been defined in several ways
*
*
the distance between two lines marked on a platinum - iridum rod preserved at
constant temperature of 273.16 k at bar pressure
o
*
The standard metre has been preserved in bureau of weight and measures at severs near paris (france )
In india , the standard metre is maintained at the
National physical laboratory in Delhi
*
*
The standard metre , is defined in terms of wavelength of ligth , as more metre equals
,
1,650,763,73
wavelength of
orange-red
light of
krypton -86
Mass :-
Mass is basic property of matter , it can bee measure of the quantity

of matter that object is contain.
*
The unit of mass in
SI

unit is the kilogram ( kg
).
*
The standard kilogram is the mass of a

platinum - tridium
cylinder stored in the
International Bureau of Standards in
Serves , France
*
Weight is a force which body is pulled to the earth
TIME :-
Time is around us and we are familier with it in qualitative terms
A natural standard for ,measurement of time is derived from the resolution of the earth
*
*
A solar day is the period between noons
(
it is the time at which the sun is at hightest point during its transit across the sk
y )
of consecutive day
*
the solar day is the average day over a year. the standard time is based on periodic vibration in a cesium atom. second corresponds vibrations
9,192,631,770
in cesium -
133
atoms
*
The National Physical Laboratory , New , Delhi

has the responsibility of maintainances and improvement of physical standards of
length , time , mass etc
*
the metre was defined ..... as the distance travels through space in ,
1
_____________
299 , 792 ,458
of a second
*
the distance of stars from the earth are expressed in light years
*
A light years is a unit of length equal to the distance travelled by light in one year
1 light year = 9.46 x 10 in
5
*
For centuries time has been universally measured in terms of the rotation of the earth. the second the basic unit of time was difined as

1/86,400
of a
mean solar day or one complete rotation of the earth on its axis.
*
Scientists
discovered the rotation of the earth was not constant enough to serve as the basic of the time standard
*
As a result , the second was redefined in terms of the resonast frequency of the cesium atom in

1967
*
Which this atoms absorbs energy or

9 , 192 , 631 , 770

hertz (cycles per second) . the second correspond to
9 ,192 ,631 ,770
- vibrations in cebium
133
atoms
*
The national physical laboratory , New Delhi has the responsibility of maintance and improvements of physical standard
of
length , time , mass
etc
TEMPERATURE
The
temperature

scale was based on a fixed temperature point , the triple point of water at which

solid , liquid and gas
are in equlibrium .
the temperature
of
273.15k
was assigned to this point and the freezing point of water was
disignated exactly 0 celsius temperature scale
o
The celsius scale , which is identical to the centigrade scale
.
named in 18th century
Swedish astrnomer
;
andres
-
celcius
celcius was first proposed to use scale in which the interval between the freezing and boiling point of water is divided to

100 degrees
.
by the international agreement the term celsius has offcially replaced by centigrade
AMPERE :-
the ampere was defined as the
constant current
that following
in two paralled conductor one metre apart in avaccum wil produce a force between the conductors on
2x10 new tons / metre of length
7
CANDELA :-
the international unit of light intensity
The candela , was originally difined as
1 / 60
of the light radiated from squre centimetre of a black body , perfece radiatior that absords no light held at the temperature of
freezing platinum .
It is defined as the intensity of a light source , in a given direction witha frequency of
540 x 10

hertz and a radiant intensity of

1 / 683

watts per sterdian in that direction
12
MOLE :-
Mole is a base unit of the international system of unit , defined as the amount of a substance that contains as many elementary particles
atoms , molecules , ions , electrons or other particles
The number of carbon atoms in
12kg of
carbon 12 , is approxismately
6.02x10

this is called
23
Then mole amount of any substance that
weights , in frams , as much as
the
numerically equivalent atomic weight of that substance
MECHANICS
Mechanics
can be defined as the field of physics that studies the effects of force on
solids, liquids and gases at rest or in motion
mechanics can diveded into two branches
kinematics and dynamics
Kinematics , studies bodies at rest or
in motion at a constant speed and in a constant direction
MASS :-
Mass is different from weight , which is a measure of the attraction of the earth for a given mass. is diffrent from weight which is a measure of the attraction of the earth for agiven mass.
ACCELERATION:-
acceleration is defined as the rate of change of
velocity
, that is , the change of velocity divided by the time interval during the change. acceleration may be measured in such units as,
metres
per second - per second
or
feet per second per second

_
_______
Time
_______
sec
2
FORCE
Force
is a measurable influence that causes something , to move. force is a vector , which means
it has both direction and magnitude
*
The idea or net force must be taken into account because forces other
than the applied or may act on the object
*
The
friction force
is always opposite to the direction of motion
FRICTION
Friction is the force which opposes the relative motion of two
surfaces in contact friction plays an important role in our lives.
it is friction between the ground and the soles of our shoes that
makes walking passible and
it is lack of friction that makes our feet slip on highly polished surface
The friction force acts when a body is moving
sliding on a surface
Sliding Friction
Sliding friction
depends on the nature of the two surfaces and not on the area of contact
. it also depends on the weight of the moving body

Heavier bodies experience more friction
W
hen cylindrical or spherical body rolls over a surface the force opposing the motion is called

rolling friction
the same pair of materials ,
rolling frictio
n is much smaller than
sliding friction . this phenomenon of friction can be reduced in the machines by using ,
1 ) lubricants
2 ) ball fearings to aquire more effeciency of the engines
when an object moves through air , frictional force oppose its motion

However , air friction is much less than liquid friction this is demonstrated by a hover craft which travels smoothly on a cushion of air
A HOVER CRAFT :-
Experiences mush less friction than a boat of the same size which has to push through water
Work ,
Power
and
Energy

Work :-
Work is said to done if the force applied on the object succeeds in moving it.

if no motion takes place, no work is said to be done . the work done is measured by the product of the force and the distanced moved in the direction of the force.

It is measured in J
OULE
( J )
work ( w ) = force ( f ) x distance ( d )
POWER
:-
the rate of doing work is called power .it is measured
by the amount of work done in one second.
it is measured in
watt
( w )
________
time taken
ENERGY :-
the capacity for doing work is called energy .
it is also measured in joule ( j )
the various forms of energy are
potential , kinetic , electrical , heat
.one from of energy can be converted into another form of energy by suitable
kinetic and potential
energies are the simplest and collectively called
mechanical energy
Kinetic energy :
the energy possessed by an object due to its ,

motion
is called kinetic energy and is describe by the expression .
__
2
2
*
Where '
m
' is the mass of the object and
v
is its speed.
*
A moving bullet or a moving stone possesse
kinetic energy.
*
Which means that if the velocity of an object is double , its
kinetic

energy
becomes four times.
*
A car travelling at
60km/hour
has four times as much
kinetic energ
y as the same car travelling at
30km/hour.
Potential Energy :
The energy possessed by an object by virtu of its
position is called
potential energy
.one of the commonest form of

potential energy
is that the energy possessed by an object when it it is above the level of the earth's surface.this called
gravitationa
l
potential energy
and is describe by expression .
*
Where
'm'
is the mass of the object
. 'g'
is the accleration due to gravity

and
'h'
the height of the object above the earth surface .
*
there are many examples of
potential energy
. water is an elevated reservior possesse p
otential energy .
*
A stretched or compressed spring also has

potential energy .
PE = mgh
Conservation of Energy :
Energy can neither be created nor destroyed
it can only be transformed from one from into another , but the total amount of energy remains constant.this is know as
conservation of energy .
*
When the stone is released is starts falling to the ground consequently it looses

potential energy

due to reduction in its position but simultaneously .
*
Kinetic energy
at the expense of
potential energy .
*
The energy spent in overcoming air friction then the loss in
PE
is exactly equal to the gain in
KE .
Hitting the ground the
mechanical energy
of the stone is converted into internal (
heat
) energy and some
sound energy.
Example :
MOLECULAR PROPERTIES OF MATTER
Diffussion :
Diffusion is the action of spreading over a wide area. in the
orther words it is mixing up of molecules of different gases , liquids , and even solids.
Example
When a bottle of perfume is opened in one coner of a room spreads over to far corner of the room .
Surface Tension :
It is the tension of the surface film of a liquid , which
tends to minimise surface area.
*
The surface of a liquid behaves like an eastic membrane and , therefore has a tendency to contract.
*
This property of liquids is called
surface tention
. and also caused by
molecular attractions.
*
Due to this property ,
insects
can easily walks on the surface of the water ,
mosquitoes breed on stagnant water.
*
When oil is sprinkled on the stagnant water its surface tension is lowered resulting the drowning and death of the larvae.
*
Liquid drops
,
rain drops
,
oil drops
,
drop of molten metals
,
dew drops
etc .or all
spherical.
given volume
,
a sphere has the minimun surface area
Capillarity :
Is the tendency of a liquid in a narrow tube or pore to rise are ,
fall as a result of surface tension.
*
If a hallow glass tube is dipped in water , the water rises in the tube.this phenemenon is
called capillarity.
*
Because water molecules are attracted to the glass more than to each other.
*
If the same capillary tube is dipped in mercury , the level of mercury in the tube is lower than the level outside because mercury molecules are less attracted to glass than to each other
The force of attraction between unlike molecules is call '' adhesion '' and that between like molecules '' cohesion ''
Example
melted wax of a candle ,
oil lamps
,
absorptions of water by plants roots
,
rising of ink in pens
ect .
works on the capillary action
Viscosity :
Viscosity is the fore which opposes the flow of the fluid.
this force acts in opposite to the direction of flow.
*
Viscosity
plays same role in fluids as does friction in solids
*
The
viscosity
of liquids , in general , falls rapidlly with temerature
Density and Relative Density
The
density
of a substance (
solid
,
liquid
, or
gas
) is defined as the mass of unit volume of the substance.
_____
volume
*
The
relative density
or (
specific gravity
) of a substance {
solid
or
liquid
} is the density of the substance in relation to the density of water at 4 c
o
Pressure :
Pressure is the force acting per unit area.
Pressure = force
____
area
*
Smaller the area, higher the pressure.
*
A sharp needle is able to pierce through a cloth
,
but a blunk rod is not able

to do
.
because
the needle provides a very small area,
and all the force applied on the needle is concentrated at the tip of the needle in the form of pressure
*
The pressure in a liquid increases with depth.
similarly pressure in a liquid

increases with the density of liquid denser liqui
d
like
(
mercury
)
exert large
pressure
*
The
pascal's law
of fluid pressure states that the pressure exerted on an enclosed liquid at one place is transmitted equally throughtout the liquid.
*
The hydraulic pree , hydraulic brake and hydraulic door closer work on the basis
of
Pascal's law

UPTHRUST
:
the upward force exerted by a liquid on a body partially or

wholly immersed in it is called
upthrust or buoyant force .

*
upthrust that makes it easier to lift an object under water
The bouyant force is higher for liquids of higher density
Example
Upthrust
is more in saline water than in fresh water
ARCHIMEDES PRINCIPLE :
The
Archimedes principle
says that how long is the buoyant force. when a solid body is wholly or
partially immersed in a fluid , it experiences an upthrust equal to the weight of the fluid displaced
by it
*
fluid means liquids and gases
*
The

Archimedes principle

is equally applicable for gages including the atmospheric air
*
A particular case of Archimede's principle is the principle of flotation
*
The weight of liquid displaced by a floating body is equal to the weight of the body
*
Why a solid iron ball sinks in water whereas a ship made of iron floats, because a ship is hallow and contains air unlike a solid iron ball and therefore of less density than water
*
The density of a liquid in which a body floats , higher its level above the liquid , since salt water is denser a ship sinks less in seawater than in river or lakes
Example :
hydrogen balloon rises up in the atmospheric air , because the air displaced by the hydrogen balloon is ledd than of its density
CRITICAL VELOCITY :
As the falling object gains velocity ( due to the downward,
force of gravity), the opposing viscous force also increase when the viscous force
equal the gravitational force and therefore , the net force on the falling object became zero, the object the stop accelerating and falls with constant velocity know as the
critical velocity
*
Sky divers can form group by joining hands. this is possible because the divers can alter their critical velocity by changing their position.
Atmospheric pressure is measured with an instrument called the
barometer.accurate measurements of atmospheric pressure in labor-
atories are made with an fortin's barometer which is an improved form of a simple mercury barometer
*
A small portable barometer , called the aneroid barometer does not use any liquid.
*
Atmospheric pressure varies with altitude, a barometer can be used for determining
altitudes is called

altimeter
*
Barometer are also used for weather forcasting.if the barometeric height falls suddenly , it indicates the coming of a storm
*
A gradual fall in the barometeric height indicates the possibility of rain
*
A gradual increase in the barometeric height indicates fair weather.
REFRIGERATOR :
In a
refrigerator
, cooling is produced by the evaporation
of a volatile liquid
,
freon
,
inside a copper coil (evaporation ) which sorrounds the freezer
RELATIVE HUMIDITY :
Relative humidity is defined as the ratio of the mass of
water vapour in a given volume of air at the same temperature, the weather report in news papers expresses relative humidity as percentage .
*
Relative humidity is measured with an instrument called the

hygrometer
PRESSURE COOKER :
The boiling point of a liquid depends on external ,
pressure.when the external pressure increase boiling point also increase. the
tendency is applicable in the pressure cooker.
In a pressure cooker , water boils at temperature higher than 100 c due to increased pressure . the increased boiling temperature allows water to hold more heat which cooks food faster

*
At higher altitudes , atmospheric pressure is low. this lowers the boiling point or water and food takes much longer to cook .thus a pressure cooker
becames more eeential for cooking on hill stations
HYDROMETER :
A hydrometer work on the basis of principle of flotation. it is used for

rapid easy of density or relative density of liquids.
*
A

lacometer

is also a hydrometer , which is used to measure the relative density of a sample of milk .
*
A common form of a

hydrometer

is a carbattery tester which measures the relative density of the acid in a battery
NEWTON'S LAWS OF MOTION
New ton's
law are three physical laws
First law :
every object continues in its states of rest or of uniform motion ,
in a stright line if no net force acts upon it.
*
An unwary passenger in a fast moving bus falls forward when it stops suddenly.this happens because the efect of the passenger come to rest
suddenly where as his body continues to be in motion
*
A person getting down from a moving bus has to run some distance , in the direction of the bus , before stopping
INERTIA :
The inertia of a body is its tendency to resist acceleration , or change
in its velocity , the mass of body is quantitative measure of its inertia .

*
It is harder to slow down , speed up , or turn a moving object
*
To make a some gradually hey object like
ship
,
lorry
require more force
to stop or more than small object like
car
,
motorcycles
etc..
*
The momentum of a body is defined as the product of its mass and velocity
momentum = mass
x
velocity
Second law :
This law states that the rate of change of momentum of a body is proportional to the applied force and takes place in the direction of the force , it implies
that force ( f ) is proportional to the product of mass ( m ) and acceleration ( a ).
F = MA
Example :
*
A car consumes more fuel on a crowded road than on a free road ,The car has to stop and start quit often on a crowded road
.
*
On a free road , car moves with a uniform speed requiring fewer accelerations , thus it requires less fuel .
Third law :
This law states that

''
for every action there is an equal and opposite reaction . ''
*
It means that if a person hits a ball against wall (
action
) , the ball returns with the same force (
reaction
)
*
When a bullet is fired from a gun , equal and opposite forces are exerted on the shoulders of the person.
IMPULSE
Change of momentum is impulse. in other words , impluse is the product if force and time. its impact depends on oth variables , mass and velocity
*
A heavy truck has more momentum than a car moving with same velocity
Impulse ( i ) = force ( f )
x
time ( t )
Example :
In a cricket match , when fielder has to catch a fast moving ball , he moves his hand along with the ball
Different Kinds of Forces
The word force generally denotes a push or a pull . we oftern perplexed
by learning about moving object in the solar system . planets satellites asteroids. etc moves around the sun without any direct contact between them.
They are few fundamental forces
Gravitational Forces :
The force that attracts a body towards the centre of the earth , or towards any other physical body having mass is know as gravitational force .
*
In fact the gravitational force exists between all bodies , even between two apples lying
on a table. it is gravitational force .
*
The moon in its orbit round the earth and , the earth in its orbit round the sun
Newton's law of Universal Gravitational :
Every particle in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
1
2
r
2
Where ' r ' is the distance between two masses m1 , m2 and G is the universal gravitational constant. the value of G is 6.67 x 10 SI units.
-11
Centripetal Force
For a body to move in a circle there must be a force on it
directed towards the centre
.this is called centripetal force
*
And it should be change direction in a circular motion
*
When a stone tied at one end of a string which whirled in a cricle ; the pull in the string provides the centripetal force
*
The moon , artifical satellites which move around the earth works on this principle only
*
The magnitude of the centripetal force ,
FC
required to cause an object of mass
m
and speed
v
to travel in a circular path of radius
r
is given by the relation
Fc = mv
____
r
2
Centrifugal Force
The radially outwards force on a body in a uniform circular motion observable only in a rotating frame of reference is called '
centrifugal force. '
It is equal and opposite to the centripetal force as it acts outwards

when a body revolves in a circle .
*
Centrifuge :
A Centrifuge is a machine used to separated particles of higher mass from lower mass in a given mixture
.
A centrifuge consists of a cylindrical vessel rotated about its own axis at high speed with the help of an electric motor
*
When milk is poured into the cylindrical vessel of the centrifuge and rotated with high speed , the particles of higher mass
( skimmed milk )
are thrown away from the centre due to greater centrifugal force and
lower - mass
cream particles collect at the centre
*
The churner sets the curds into swift rotatory motion and hence the lower mass butter is collected at the churner
*
With the help of
centrifuge
,
honey is separated from bee's wax
Laundry Drier
In a Laundry drier , the wet clothes are dropped into a cylindrical vessel containing
holes.
When the vessel is rotated , the wet clothes get stuck to the walls of the vessel.
*
*
The centrifugal force pushes the water molecules from the clothes out through the holes.

thus clothes are dried
BANKING OF ROADS AND RAIL TRACKS
If there is curvature for the road ahead, car has to take a turn. this means that the car has to move on an arc of a circle, then naturally a, centripetal
force is necessary to make the car to travel on the curved road
*
The centripetal force is provided by raising the outer edge of the road slightly above the level of the inner edge towards the centre of the curvature of radius say r ).this
is know as banking of roads
Banking of rail tracks :
If there is a curvature for the track a head , the train has to
taken a turn.this means that train has to move on a curved track
*
The centripetal force necessary to make the train travel on the curved track is provided by raising the outer rail slightly above the level of the inner rail towards the centre of the curvature of radius ( say r ) . this is know as banking of rail tracks
KINEMATICS
The equation of motions of a body travelling with uniform acceleration.
They are some equations :
v = at . . . . . . ..
1
1
__
2
at 2 . . . .. .
2

v 2 - u 2 = 2as . . . . . .
3

Initial velocity (u )
Final velocity ( v )
Uniform acceleration ( a )
Distance ( s )
Time ( t )
s = ut +
Motion of a body under gravity acceleration due to gravity ' g '
The earth exerts a gravitational force on all bodies . at any given place the acceleration
due to this force , ' g ' is a constant . it is directed towards the earth. therefore , bodies
moving under gravity will subjected to this uniform acceleration due to gravity ' g ' .
*
Equation 1 to 3 can be used for bodies in motion under gravity by replacing the
acceleration ' a ' by ' g '. the body travel vertically 's' may be replaced by the height ' h ' .

Note that

' + '
and
' - '
signs have to be used in the case of bodies moving towards and away from the earth respectively.
they are two cases
1 ) a body falling freely and
2 ) a body thrown upwards
v = u gt . . . . . (4 )
h = ut
1
__
2
-
-
2
2
2
Equations of motion for a freely falling body
Imagine that you are on the top of a tower or inside a moving aeroplane . when a body is dropped from the tower or slipd out of the plane , no
initial force is applied. the body falls with uniform acceleration ' g ' under
the action of gravity know as freely falling body
*
For a freely falling body , with initial velocity ,
u = 0
, the velocity continuously increase as it falls through a height.
*
The direction of
'
g
'
motion of the body are same

(i .e., downwards )
v = gt . . . . . ( 7 )
h
v
Hence
, equations of motion
4 to 6
can now be written as
1
2
__
2
2
Equations of motion for a body thrown upds
Can a body move away from the earth on its own . . ? it is impossible because of the
gravitational attraction .
*
If you want a body to move upwards , you have to use force and throw it up with an initial velocity ' u ' .
*
The body ll not go up indefinitely but will fall back after reaching a certain height , because ,
its velocity continuously decreases and finally becomes zero .
*
*
The acceleration due to gravity ' g ' acts in a direction opposite to the motion of the body .
v = u - gt . . . . . . ( 10 )
1
___
2
2
The equation
4 to 6
can be changed as
v
2
2
Maximum Height Reached by a Body Thrown up
Let a body be projected vertically upwards with an initial velocity u . since , it is moving
upwards , its acceleration is ' -g ' , the body goes up , its velocity decreases and finally becomes zer ( v = 0 ) at some point ( h )
*
This
' h '
point is the maximum height reached by the body , using relation
(12 )
for bodies
projected upwords .
2
Hence
,
maximum height attained by the body is directly proportional to the square of the
initial velocity
' u '
Time of Ascent :
The time taken by body thrown up to reach maximum height

' h '
is called its time of ascent
*

be the time of ascent , at the maximum height , its velocity

v = 0

1
Hence
, from equation ( 10 )
Time of Descent :
The time of ascent is equal to the time of descent in the case

of bodies moving under gravity
t
2
u
__
g
t
1
u
__
g
Hence
,
time of ascent

is directly proportional to initial velocity
1
Time of Flight :
Time of flight
is the time for which a body remains in the air is given by the sum of time of ascent and time of descent .
Hence ,
or
Time of flight =
1
2
U
g
2u
g
__
___
U
___
g
. .. . . . (16 )
Velocity on reaching the ground
When a is dropped from a height h , its initial velocity is zero. let the final velocity
on reaching the ground be v . for a freely faling body , from equation ( 6 ) .
V = √2gh
. . . . . . ( 17 )
Further , from equation ( 13 ) for the case of a body thrown upwards , we
have for initial velocity .

U = √2gh
. . . . . .. . ( 18 )
The upward velocity at any point in its flight is the same as its downward velocity at that point .
Quantity
Unit
Symbol
Force newton N
Work joule J
Energy joule J
Heat energy joule J
Power watt W
Frequency hertz Hz
Electric charge coulomb C
capacity fared F
Inductance henry H
Resistance ohm Ω
Electric potential volt V
Magnetic flux weber WB
Magnetic flux density tesla T
Luminous flux lumen lm
Illumination lux lx
Heat

Heat

is a form of energy and is called
thermal energy
.
heat
and tem-
perature are closely related in that ,
heat
is the cause and temperature its effects. temperature is measurable manifestation of the
thermal energy of a body
Measurement of temperature and scales
The temperature of a substance is measured in a thermal mometer .
They are three different scales are used
*
1 ) Cesius scale ,
2) Fahrenheit scale
3 ) kelvin or (obsolute ) scale
Celsius scale :
This scale was invented by the swedish astronomer
celsius . on this scale
the lower fixed point is taken to be o c .which
pure melting ice and the upper fixed point is marked 100 c.
were
temperature of boiling water at sea level.the intervel between them is divided into 100equal degrees.
0
0
Fahrenheit scale :
This scale was suggested by
Fahrenheit
and commo-

nly used for clinical purpose.on this scale the lower fixed point is marked 32
F
and corresponds to
0 C
and the upper limit is marked
212 F
which
corresponds to 100 C. the Conversion table from Celsius to Fahrenheit
and vice verse is
9C = 5 ( f - 32 )
. at
''-40''
both the Celsius and the
Fahrenheit scales are equal
0
0
0
0
Kelvin scale :
This scale was developed by lord kelvin. unlike the
other two scales, this scale is used to measure very low temperature. this
scale has been calibrated on the basis of obsolute zero is minimum temperature, can theoretically exist in the universe .
Absolute zero is
minus 273.16 c on the celsius scale . this has been taken as o k ( it is not
o k ) and 273.16 k corresponds to 0 c and 373.16k to 100 c

0
0
0
Clinical Thermometer :
This thermometer has been specially designed for
measure the temperature of the human body .
the normal temperature of the human
body is 36.9 c or 98.4 F , therefore this thermometer has a short range of 95 F to
110 F ( 35 c to 43 C ).
Another special feature , there is a constriction in the tem of the capillary tube near
the bulb , and expanded mercury of fall back into the bulb unless a slight jerk is given to the thermometer .
0
0
0
0
0
0
Thermal expansion
When the temperature is increased , two important effects are
observed in matter, they are the increase in size and the change of
state

( melting and boiling )
If any state
( solid , liquid , or gas )
are heated and they expands .
Given temperature , gases expands more than liquids and liquids
expand more than solids
Thermal expansion of solids
The thermal expansion of solids has both bad and good effects .in order to
avoid the bad effects , certain precautions are taken .
Example :
a )
gaps are allowed between two successive rails for the rails to expand.if no gap is provided ,
in summer due to expansion the rail would bend. similarly gap is provided in long iron bridges .
b )
Telegraph wires are never kept tight
*
The useful application of thermal expansion of solids are
( i )
iron and steel tyres are tightly fit on cart - wheel by initially heating them
A thermostat also works on the basis of thermal expansion of solids .
Anomalous thermal expansion of water
Liquids on heating , expands uniformally i.e., their volume increase linearly with temperature .but water is an exception to this general rile. it shows unusual ( or
anomalous ) behavior . when water at o C is heated , in the temperature range of 0 C to 4 C it contracts instead of expanding . on further heating beyond 4 C , like other liquids , it starts expanding . water , therefore , has its minimum volume and maximum density at '' 4 C ''
*
The peculiar expansion of water has a significant effect on aquatic life during very cold
weather.
*
In cold countries , as the temperature of atmosphere falls , the top layer of a pond or lake cools first
*
When the temperature of the top layer of water falls below 4 C it expands and becomes less dense and therefore no longer sinks and ultimately it freezes
*
0
0
0
0
since in ice a poor conductor of heat , it prevents the loss of heat from the pound
and helps in keeping the water below at 4 C ,the entre pond does not freeze.

0
Measurement of the temperature
Temperature is defined as the degree of hotness and or coldness of a body. A thermometer is a device used to measure the temperature of the body
They are three thermometer scales used
centrigrade or celsius ( c )
Fahrenheit ( f ) and
,
Kelvin ( k )
,
The
is graded on the decimal scale and is therefore easiest understood .
freezing is the zero ( o ) point and boiling water is 100 degrees.
In the
fahrenheit
scale the zero point is 32 below the freezing point of water.the
boiling point of water on this scale is 212
0
0
Zero degrees on the kelvin scale is taken as the lowest possible temperature
, called absolute zero which is
-273.16 C or -459.67 F .
0
0
The size of the degeree in the kelvin scale is the same as in the celsius scale.
so in the kelvin scale water freezs at
273.16 K
o
Changes of scales :
0 C = 273 K
o
o
1 F =
5
9
5
9
0
0
__
__
x
0
1 F
x
1 F
0
To change from centrigrade to fahrenheit. :
Multiply centrigrade degree by 9 , divided the result by 5 and add 32 .
To change from fahrenheit to centrigrade :
Reverse the above equation .that is substract 32 from fahrenheit degree ,
multiply by 5 and divided by 9

Mercury is used in thermometer because it is a liquid over a fairly wide
range of temperature . it freezs at -39 C and boils at 357 C . it is readily
seen and the expansion is regular

Transmission of heat :
heat can be transimtted in three different ways ,
conduction
Convection and
Conduction is the process by which heat is transmitted in solids by the
drifting of their free electrons .
The transfer of heat takes place in all substances , but the rate heat transfer is different for different substances.
*
The substances through which heat is easily transmitted are good conductor.
*
Metals are generally good conductors of heat .
*
On the other hand , substances such as cork , wool , cotton are poor or bad conductor
Of heat .
*
Liquid s and gases in general are bad conductors .
*
Substances such as asbestos, ebonite are worst conductors of heat and are called insulators .
some tables listed various common substance in their order of heat conductivity
Substance
Heat conduction rating
Silver 100
Copper 90
Aluminium 50
Iron 12
Mercury 2
Glass 0.15
Asbestos 0.06
Wood 0.05
water 0.015
cork 0.010
Cotton wool 0.0005
Air 0.005
Convection is the process by which heat is transmitted in liquid and gases
In this process he is carried from one place to another by the actual movement of liquid and gases .
When a gas or a liquid is heated from below , the heated particles become lighter and ,
move towards the top , while the colder particles , being heavier sink to the bottom .
Ventilation in a room , is possible because of the convection currents set in the room .
In a refrigerator , the cooling unit , called freezer is set at the top . when air is cooled it becames heavier and sinks and thus sets up a convection current inside the refrigerator enabling uniform cooling .
But in geyser , the heating element is set at the bottom , because otherwise a convection current cannot be set to heat water in its entirety .
The Uneven heating of the earth by the sun are responsible for sea , land and monsoon winds .
Radiation is the process by which heat is transmitted in the absence of matter
Therefore , unlike conduction and convection , radiation does not need a medium to propagate heat and it can be trasmitted in vaccum .
The sun's energy reaches us by radiation in the form of electron magnetic waves .
If a body obsords more energy than it emits , its temperature rises .
The amount of heat energy radiated or absorded by a body depends on its
temperature , nature and area of its surface .
Given temperature , a rough surface absords or emits heat faster than that of a polished surface .
A black body absords and emits heat faster than a light coloureed body .
Which a hot body loses heat is directly proportional to the difference between its temperature and the surrounding temperature .
Example
:
Hot water takes less time in colling from
90 C to 80 C than from 50 C to 40 C .

0
0
0
0
Like all the other planets the earth receives , during the day , the radiant energy of the sun . this is known as insolation
At the night earth starts emitting the radiant energy it received during the day and becomes cool .
The night is cloudy , then the night temperature is warmer than usual . this is so because , clouds reflects the earth 's radiation back to the earth and so the earth loses little heat .
The day is cloudy , temperature is less and clouds reflects the sun's rays back to the space .
Fluctuation in the day and night temperature in deserts.
it is a special kind of a bottle or flask which is designed in
such a way that its keep cold things and heat things for a considerable time .
The vacuum flask consists of a double -walled glass vessel .
The space between the walls is evacuated of air to create on the vacuum side . the mouth
of the bottle is fitted with a cork stopper .
The contents of the flask can not take in or give out heat to the surroundings
The outer wall of the inner vessel is

highly silvered
,
it became a poor radiator of the heat
energy
.
The inner wall of the outer vessel is also highly polished , it becomes a good reflector
The walls reduces the heat transfer due to radiation to a minimum .
Evaporation :
The conversion of a liquid into vapour , without necessarily
reaching the boiling point is called evaporation , when evaporation takes place at room temperature , the heat required to vapourise is taken from the liquid
itself and therefore evaporation result in cooling .
*
A pitcher in summer , keep its water content cool , as evaporation taking the body heat and
produces a cooling sensation.
Evaporation of a liquid depends on four factors :
a ) The higher temperature of the liquid , higher rate of the evaporation .
b ) larger area of evaporation of a surface , higher rate of evaporation .
c ) Faster rate of removal of vapour , higher rate of evaporation .(
a fan produces a larger
effect for the same reason. )
d ) Drier the medium in which evaporation takes places, faster rate of evaporation .
The atmosphere air is saturated with water vapour and reduces the rate of evaporation .
Evaporation and Boiling :
Evaporation
takes place from the surface of any liquid exposed to air temperature , whereas boiling takes place at a given temperature called the boiling point of the liquid under given pressure .
*
The former is a slow process , but the later is a rapid process .
*
Evaporation takes place at the surface of a liquid , whereas boiling takes place in the entire body of the liquid .
MOTION
There are Four Types of Motions
Periodic Motion :
Any motion that repeats itself along the same path in equal intervals of time is called a
periodic
motion

Oscillatory Motion :
If a periodic motion moves back and

forth over the same path , its motion is said to be
oscillatory
or vibratory motion

Examples
The motion of pendulum of a wall - clock .
Motion of strings in musical instruments like violin , guitar etc .
The invisible motion of atoms in a soild.
Simple Harmonic Motion
The to - and - for motion of a particle about a mean position on a fixed path such that the acceleration of the particle is always directed the mean
position and is directly proportional to the displacement of the particle from
its mean position is called a simple harmonic motion .
( Acceleration )
=
Velocity
=
Metre
Power
=
Work done
KE
=
1
mv
Density
=
Mass
F
=
m
m
_____
+
+
-
v
v
=
+
2gh . . ( 6 )
-
gt . . . ( 5 )
=
gt..... ( 8 )
=
2gh . . . . ( 9 )
h
=
ut
-
gt
-
u
=
- 2gh . . . ( 12 )
. . . . . ( 11 )
v
2
-
u
2
=
- 2gh
0
-
u
2
=
-2gh
h
=
u
___
2g
. . . . . . ( 13 )
=
. . . . . ( 14 )
( t )
=
let
' t '
t
=
t
+
t
t
=
1 C
=
*
Time period ( t ) is independent of amplitude , and independent
of mass of the body . time period is directly proportional to the square root of the length of the pendulum .
Wave Motion :