PHYSICS
1.
Measurements and Units
The unit of length
is metre. (m) Other units of length are foot,
yard.
Fundamental Quantities
Certain quantities are independent and they remain
as basic quantities. They are called fundamental
quantities.
Fundamental Units
Fundamental Units are units of fundamental quantities.
Derived Units
Derived Unit is a unit got by the combination
of fundamental units.
International System of Units (SI units)
SI units comprises of seven Fundamental Units
and two supplementary units internationally.
Fundamental Units
in SI System
Physical Quantity Basic Unit Symbol
1. Length Metre m
2. Mass kilogram kg
3. Time second s
4. Electric Current ampere A
5. Temperature Kelvin K
6. Luminous Intensity candela Cd
7. Amount of matter Mole mol
10 mm 1 cm
10 cm 1 decimetre
10 decimetre 1 m
10 m 1 decametre
10 decametre 1 hectometre
10 hectometre 1 kilometre
Astronomical unit (AU) is the average distance
of the sun from earth.1 AU = 149,597,890 km.
Light Year is the
distance traveled by light in 1 year.1 light year
= ( 3,00,000 km/s ) X (60 x 60 x 24 x 365)s =
94,60,80,00,00,000 km.
1 cm3 1 milli litre
(1ml)
1000 ml or 1000 cm3 1 litre
1000 litre 1 m3
Derived SI Units
Other units
Area m2 cm2 , mm2
Volume m3 (cubic metre) cm3 , litre
Density =Mass/Volume kg / m3 g / cm3
Area
The SI unit of area is m2. It is the area of a
rectangle having a length 1m and breadth 1m.
Volume
The SI unit of volume is m3. It is the volume
of a cubical structure having a length 1m, breadth
1m and height 1m.
Mass
Mass is the quantity of matter contained in a
substance.
Density
Density is the mass of the body contained in unit
volume.
Materials Density
(kg/ m3)
Gold 19 600
Uranium 18 500
Lead 11 400
Copper 8 900
Iron 7 900
Rock(average) 2 600
Aluminum 2 700
Magnesium 1700
Water 1000
Petrol 750
Kerosene Oil 800
Cork 250
Time
Very small intervals of time are to be measured
by stopwatches and stop clocks.
Least Count
We make use of metre scale for measurement of
length. Smallest measurement of the scale is 1mm.
P.1. Find out the
Least Count of the thermometer and clinical thermometer
2. Refraction of
Light
Light Ray
Light travels along a straight line. A ray in
fact, represents a narrow beam of light.
3. Lenses
4.
Motion
We are traveling
along with the earth in its rotatory and revolutionary
motions at a speed of 30km/s.
Motion is relative.
Distance and Displacement
The idea of displacement is complete only if direction
is also mentioned.
Speed = Distance/Time
Velocity = Displacement/time
= Displacement in unit time. (Displacement involves
direction and is measured in metres and time in
seconds)
Unit of velocity is m/s
Acceleration (a)
= Change in velocity/time (acceleration represents
increase in velocity and decrease in velocity
is retardation or negative acceleration)
u – initial
velocity
v – velocity after t seconds
Unit of Acceleration is m/2
Uniform motion and non-uniform motion
The type of motion covering equal distances in
equal intervals of time is uniform motion.
Vectors
Some measurements will be complete only if their
directions are mentioned. Such measurement is
called vectors.
Scalars
Measurements which do not require direction are
called scalars.
Average Velocities of Certain moving objects
Snail 5.4 m/h
Pedestrain 5 km/h
Fish 3.6 km/h
Fly 18 km/h
Eagle 86 km/h
Sound in air 1200 km/h
Supersonic Plane 3000 km/h
Revolution of the earth 1,08,000 km/h
5.
Wave Motion and Sound
Different types of Motion
· Rectilinear motion
· Rotatory motion
· Revolutionary motion
Periodic Motion
Motions which repeat at fixed intervals of time
are periodic motions.
Vibrations or Oscillations
Periodic motions of the following types are generally
called vibrations or oscillations.
(Exciting the string of a guitar or veena)
Wave Motion
Wave motion is one of the different ways by which
energy is carried from one place to another.
· Transverse waves
o Waves have humps and dips.
o The hump is called the crest of the wave and
dips are known as trough.
o One wave is formed by a crest and a trough.
· Longitudinal waves:
o Particles move in the direction of motion of
waves. Waves of this type are called longitudinal
waves.
o When longitudinal waves pass through a medium
and rarefactions are created alternately. (A compression
is a region of increased pressure and rarefaction
is a region of decreased density.)
o In this case, wavelength is the distance between
two successive compressions and rarefactions.
Wave length (lambda)
The distance between the successive crests of
the wave is the wavelength and is denoted by the
Greek letter lambda.
Amplitude (a)
The distance of the highest point of the wave
from the undisturbed surface of water is noted
as amplitude.
Wave velocity (v)
Wave velocity is the distance that a wave travels
in one second.
Frequency (f)
Frequency is the number of crests or troughs crossing
a point in one second. This is same as the number
of waves passing a point per second. The unit
of frequency is hertz (Hz).
1 kilo hertz (kHz) = 1,000
Hz
1 Mega hertz (MHz) = 1,000,000Hz
The kinetic energy of the stone when it falls
into water is carried by the spreading waves.
Water acts as the medium for wave motion. Thus
waves cause the energy to reach the thermocol.
Heinrich Rudolf
Hertz 18571894
Hertz was a Germen scientist who first produced
and transmitted the electromagnetic waves.
6. Static Eletricity
Electricity by rubbing
Substance acquires electric charge by rubbing
or friction.
What causes attraction?
Atoms have in them positively charged protons
and negatively charged electrons. They attract
each other.
When two suitable substances
are rubbed against each other, electron transfer
takes place from one substance to the other. The
substance that gets electron becomes negatively
charged and that which looses electron become
positively charged. The charge remains at the
position where they were transferred to the object.
Therefore these charges are called static electricity.
· When glass is rubbed against silk ----à
Electrons transferred from glass to silk.
· Electric charge is measured by the unit
of coulomb.
· The charge of an electron is very very
small.
· 6.25 X 1018 electrons =1 coulomb
7.
Current Eletricity
8.
Heat
|
