SI unit of
Force- Newton(CGS=dyne), 1 newton= 105 dyne.
Si unit of
Work- Joule(CGS=erg), 1 joule= 107 erg.
Cream
separator, centrifugal drier work on the principle of the Centrifugal force.
SI unit of
Power- watt.
Value of g=9.8
m/s2 decreases with height or depth from earth’s surface.
Value of g is
maximum at poles.
Value of g is
minimum at equator.
Value of g
deceases if the angular speed of earth increases and increases if the angular
speed of earth decreases.
If the angular
speed of earth becomes 17 times its present value, a body on the equator
becomes weightless.
Sudden fall in
barometric reading is the indication of storm.
Slow fall in
barometric reading is the indication of rain.
Slow rise in
the barometric reading is the indication of clear weather.
Atmospheric
pressure decreases with altitude, this is why it is difficult to cook on the
mountain, and the fountain pen of a passenger leaks in aeroplane at height.
Escape velocity
for earth= 11.2km/s, for moon= 2.4 km/s.
Pressure at a
point in a liquid is proportional to the depth of the point from the free
surface.
Pressure at a
point in a liquid is proportional to the density of the liquid.
Hydrolic
lift, Hydrolic Press, Hydrolic brake
works on the Pascal law.
Archimedes
Principle: when a body immersed partly or wholly in liquid, there is an
apparent loss in the weight of the body which is equal to the weight of liquid
displaced by the body.
Meta Centre:
when a floating body is slightly tilted from equilibrium position, the centre
of buoyancy shifts. The point at which the vertical lines passing through the
new position of center of buoyancy meets with the initial line is known as meta
center.
Relative
density is measured by Hydrometer.
The density of
sea water is more than that of normal water. This explains why it is easier to
swim in sea water.
When ice floats
in water, its 1/10th part remain outside the water.
If ice floating
in water in a vessel melts, the level of water in the vessel does not change.
Purity of milk
is measured by Lactometer.
The height by
which liquid ascends or descends in a capillary tube depends upon the radius of
the tube.
A piece of
blotting paper soaks ink because the pores of the blotting paper serve as
capillary tubes.
The oil in the
wick of a lamp rises due to capillary action of the threads in the wick.
The root hairs
of plants draws water from the soil through the capillary action.
To prevent loss
of water due to capillary action, the soil is loosened and split into pieces by
the farmers.
If a capillary
tube is dipped in water in an artificial satellite, water rises up to the other
end of the tube because of its zero apparent weight, how long the tube may be.
Action of towel
soaking up water from the body is due to capillary action of cotton in towel.
Melted wax, in
a candle rises up to wick by capillary action.
If a clean and
dry needle is very slowly kept on the surface of water, it floats due to
surface tension.
The addition of
detergent or soap decrease the surface tension of water and thus increases the
cleaning ability.
Bubbles of soap
solution are big because addition of soap decreases the surface tension of
water.
When kerosene
oil is sprinkled on water, its surface tension decreases. As a result the larva
of mosquitoes floating on the surface of water die due to sinking.
Warm soup is
tasty because at high temperature its surface tension is low and consequently
the soup spreads on all parts of the tongue.
Viscosity is
the property of liquids and gases both.
The viscosity
of a liquid is due to the cohesive force between the molecules.
The viscosity
of a gas is due to the diffusion of its molecules from one layer to another
layer.
Viscosity of
gases is much less than that of liquids. There is no viscosity in solids.
With rise in
temperature, viscosity of liquids decreases and that for solids increases.
Viscosity of a
fluid is measured by its coefficient of viscosity. It SI unit is decapoise or
pascal second.
Venturimeter, a
device used to measure rate of flow of fluid, works on Bernoulli’s theorem.
Speed of sound
is maximum in solids and minimum in gases.
Unit of
loudness- bel, phon, decibel.
To hear echo,
the minimum distance between the observer and the reflector should be 17m.
Persistence of
ear (effect of sound on ear) is 1/10sec.
If Mach number>1,
body is called supersonic.
If Mach
number>5, body is called hypersonic.
Bow waves: when
a motor boat in a sea travels faster than sound, then wanes just like shock
waves(in air) are produced on the surface of water. These waves are called bow
waves.
Electromagnetic
waves are transverse, hence the light is transverse wanes.
Wave nature of
light explains rectilinear propagation, reflection, refraction, interference,
diffraction and polarization of light.
Speed of light
was 1st measured by Roemer.
Light takes
8min 19sec to reach from sun to earth.
The light
reflected from moon takes 1.28 second to reach earth.
Concave mirror
uses—shaving glass/ reflector for the head lights of a vehicle, search light/
in ophthalmoscope to examine eye, ear, nose/ in solar cookers.
Convex mirror
uses—in rear mirror of vehicles since it provides erect images/ in sodium
reflector lamp.
Examples of total internal
reflection—sparkling of diamond/ mirage and looming/ shining of air bubble in
water/ shining of a smoked ball or a metal ball on which lamp soot is deposited
when dipped in water/ in optical fibres.
Myopia or short
sightedness—elongation of eye ball along the axis/ shortening of focal length
of the eye lens/ over stretching of ciliary muscles beyond the elastic limit.
Cure—Diverging lens.
Hypermetropia
or long sightedness—shortening of eye ball along the axis/ increase in the
focal length of eye lens/ stiffening of the ciliary muscles. Cure—Converging
lens.
Presbyopia—this
defect is generally found in elderly person. Due to stiffening of ciliary
muscles, eye loses much of its accommodating power. As a result distant as well
as nearby objects cannot be seen. Cure—Bifocal lens.
Astigmatism—this
defect arises due to difference in the radius of curvature of cornea in the
different planes. As a result rays from an object in one plane are brought to
focus by eye in another plane. Cure—Cylindrical lens.
Kilowatt
hour—it is the unit of energy and is equal to the energy consumed in the
circuit at the rate of 1 kilowatt (1000 J/s) for 1 hour.
|
Particle
|
Mass(Kg)
|
Charge(Coulomb)
|
Discoverer
|
|
Proton
|
1.672 x 10-27
|
1.6 x 10-19
|
Rutherford(Golastin)
|
|
Neutron
|
1.675 x 10-27
|
0
|
Chadwick
|
|
Electron
|
9.108 x 10-31
|
-1.6 x 10-19
|
J.J. Thomson
|
|
Positron
|
9.108 x 10-31
|
1.6 x 10-19
|
Anderson
|
|
Neutrino
|
0
|
0
|
Pauli
|
|
Pi-meson
|
274x9.108 x
10-31
|
+ve/-ve
|
Yakawa
|
|
Photon
|
0
|
0
|
|
Radioactivity
was discovered by Henry Becquerel, Madame Curie and Pierre Curie for which they
jointly won Noble Prize.
Nucleus having
protons 83 or more are unstable. They emit alpha, beta and gamma particles and
become stable.
Robert Pierre
and Madame Curie discovered a new radioactive element—radium.
End product of
all radioactive substances after emission is lead.
Radioactivity
is detected by Geiger Muller Counter.
Cloud
Chamber—is used to detect the presence and kinetic energy of radioactive
particles. It was discovered by C.R.T. Wilson.
Fast Breeder
Reactor- a nuclear reactor which can produce more missile fuel than it
consumes.
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