BASIC PHYSICS
Scalar Quantities
Physical quantities which have magnitude only. e. g. , Mass, speed, volume, work, time, power, energy etc, are scalar quantities.
Vector Quantities
• Physical quantities which have magnitude and direction both.
e. g. , Displacement, velocity, acceleration, force, momentum, torque etc. Moment of inertia, pressure, refractive index, stress are tensor quantities.
Newton's Laws of Motion
First Law - Every body maintains its initial state of rest or motion with uniform speed on a straight line unless an external force acts on it. It is also called of Galileo's law or law of inertia.
• When a running horse stops suddenly the rider bends forward.
• While jumping from a slowly moving train/bus one must run for a short while in the direction of motion.
Second Law - The force acting on an object is directly proportional to the product of the mass of the object and the acceleration product on it.
| Bogies of the trains are provided with buffers to avoid severe jerks during shunting of trains. |
Third Law To every action, there is an equal and opposite reaction.
• During firing the bullet of the gun recoils back.
• Rocket moves up due to reaction of downward ejection of gas.
Circular Motion
• When an object moves along a circular path, its motion is called circular motion. The external force required to maintain the circular motion of the body is called Centripetal force.
• Centrifugal force is such a pseudo force. It is equal and opposite to centripetal force.
• Cream separator, centrifugal drier work on the principle of centrifugal force. In the death well the walls of well exert an inward force over the motorcycle and as a reaction, the motorcycle exert an outward force on the walls of the well.
Friction
It is the opposing force that is set up between the surface of contact, when one body slides or rolls or tends to do so on the surface of another body.
• Due to friction we are able to move on the surface of earth.
• The brakes applied in automobiles work act only to friction.
Work
Work is said to be done, if force acting on a body is able to actually move it through same distance in the direction ofthe force. Its unit is a joule.
Work = Force x Distance
If a body gets displaced by S, when a force F acts on it; then the work done W = FS cosθ. Where θ is the angle between the direction of force and displacement. If θ> 90°, then work will be negative.
If θ < 90°, then work will be positive.
If θ = 90°, then work will be zero.
If a coolie carrying a load on his head is moving on a horizontal platform, then theoretically he is not doing any work because θ = 90°.
Energy
Capacity of doing work by a body is called its energy. Energy is a scalar quantity and its unit is Joule. Mechanical energy is Of two types.
• Kinetic Energy (K) Energy possessed by a body due to its motion.
K = 1/2 mv2
where, m is mass and v is the velocity.
• Potential Energy (U) The capacity of doing work developed in a body due to its position or configuration.
U = mgh
m is mass, g is acceleration to gravity, h is height.
| Energy of stretched or compressed spring, energy of water collected at a height and energy of spring in a watch are examples of potential energy. |
 |
| Some Equipment used to Transform Energy |
Power
Rate of doing work is called power its unit is watt.
Power = Work/Time
| ▪︎1 watt hour = 3600 joule ▪︎1 kilo watt hour 3.6 x 106 ▪︎1 HP 746 watt |
Gravitation
▪︎ Every body in the universe attracts other body by a force called force of gravitation. The gravitational force of earth is called gravity.
▪︎ The acceleration produced in a body due to force of gravity is called acceleration due to gravity (g) and its value is 9.8 m/s 2 . Acceleration due to gravity is independent of shape, size and mass of the body.
▪︎ Value of g decreases with height or depth from earth surface.
▪︎ g is minimum at poles.
▪︎ g is minimum at equator.
▪︎ g decreases due to rotation of earth.
▪︎ g decreases if angular speed of earth increases and increases if angular speed of earth decreases. The acceleration due to gravity at the moon is one-sixth that of the earth. So, the weight of a person on the surface of the moon will be one-sixth of his actual weight on earth.
Satellite
• Satellites are natural or artificial bodies revolving around a planet under its gravitational attraction.
• Moon is a natural satellite while INSAT-B is an artificial satellite of earth. The period of revolution of satellite revolving near the surface of earth is 11 hour 24 minutes (84 minutes).
• Geo-stationary satellite revolves around the earth at a height of 3600 km. The orbit of geo-stationary satellite is called parking orbit.
• Geo-stationary satellite revolves in equatorial plane from West to East. Time period of rotation of geo-stationary is 24 h.
• The earth rotates on its axis from West to East. This rotation makes the sun and the stars appears to be moving across the sky from East to West.
• Geo-stationary satellite is used to reflect TV signals and telecast TV programmes from one part of the world to another in weather for casting in predictions of floods and droughts.
• Polar Satellite revolves around the earth in polar orbit at a height of 800 km (app.) Time periods of these satelites is 84 min. These are used for weather forecasting, happing etc.
Escape Velocity
Escape velocity is that minimum velocity with which a body should be projected from the surface of earth, so as it goes out of gravitational field of earth and never return to earth.
• Escape velocity is under root 2 times the orbital velocity.
• Escape velocity at the earth's surface is 11.2 km/s.
• Escape velocity at the moon's surface is 2.4 km/s. Due to low escape velocity there is no atmosphere on the moon.
Waves
A wave is a disturbance which propagates energy from one place to the other without the transporation of matter.
Waves are broadly of two types
(i) Mechanical wave (longitudinal wave and transverse wave) (ii) Electromagnetic wave
Longitudinal Waves
In this wave the particles of the medium vibrate in the direction of propagation of wave.
Waves on springs or sound waves in air are examples of longitudinal waves.
Transverse Waves
In this wave the particles of the medium vibrate perpendicular to the direction of propagation of wave.
Electromagnetic Waves
• The waves which do not require medium for their propagation i.e., which can propagate even through the vacuum are called electromagnetic waves.
• Light and heat are the examples of electromagnetic waves. This wave propagate with the velocity of light.
• Cathode rays, Canal rays, a-rays, ß-rays, sound waves and ultrasonic waves are not electromagnetic waves.
Sound Waves
Sound waves are longitudinal mechanical waves. Based on their frequency range sound waves are divided into following categories.
• The sound waves which lie in the frequency range 20 Hz to 2000 Hz are called audible waves.
• The sound waves having frequencies less than 20 Hz are called infrasonic.
• The sound waves having frequencies greater than 2000 Hz are called ultrasonic waves.
Uses of Ultrasonic Waves
(i) For sending signals, (ii) For measuring the depth of sea, (iii) For cleaning cloths, aeroplanes and machinery parts of clocks, (iv) For removing lamp-shoot from the chimney of factories, (v) In sterilizing of a liquid, (vi) In ultrasonography.
Mach Number
It is a dimensionless quantity, which is a ratio of the speed of the object is a medium of the speed of the sound in the particular medium.
General Properties of Matter
Elasticity
Elasticity is the property of material of a body by virtue of which the body acquires its original shape and size after the removal of deforming force.
Steel is more elastic than rubber.
Pressure
Pressure is defined as force acting normally an unit area of the surface.
Pressure = Force/Area
Its unit is N/m 2. It is a scalar quantity.
•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 is measured by barometer.
•The pressure exerted by liquid column at the surface given as p = hdg, where d is the density of liquid, h is height of liquid column.
•In a static liquid at same horizontal level, pressure is same at all points.
•Pressure at a point in a liquid is proportional to the density of the liquid.
Archimedes' Principle
When a body is immersed partly or wholly in a liquid, there is an apparent loss in the weight of the body which is equal to the weight of liquid displaced by the body.
▪︎The weight of water displaced by an iron ball is less than its own weight. Whereas water displaces by the immersed portion of a ship is equal to its weight. So, small ball of iron ball sink in water but large ship float. ▪︎A fat person will quickly learn the swimming as compared to a slim person because he will displace more water so will be more balanced. ▪︎Hydrogen filled ballon float in air because hydrogen is lighter than air. ▪︎A person can lift more weight in water. |
Laws of Floatation
A body floats in a liquid if
(i) the density of materials of body is less than or equal to the density of liquid.
(ii) the density of material of body is equal to density of liquid, the body floats fully submerged in liquid in neutral equilibrium when body floats in neutral equilibrium the weight of the body is equal to the weight o displaced liquid.
(iii) the centre of gravity of the body and centre of gravity of the displaced liquid should be in one vertical line.
Density
•Density is defined as mass per unit volume.
•Relative density is measured by hydro- meter.
•The density of sea water is more than that of normal water
•The density of iron is more than that of water but less than that of mercury. So, a solid chunk of iron sink in water but float in mercury.
•If ice floating in water in a vessel melts, the level of water in the vessel does not change.
Surface Tension
•Surface tension decrease with rise in temperature and become zero at the critical temperature.
•The surface tension of clean water is higher than that of a soap solution.
•Formation of lead shots, spraying result in coldness, floatation of needle on water, dancing of camphor on water, are based on surface tension.
•Liquid drop from spherical shape due to surface tension.
•When kerosene oil is sprinkled on water, its surface tension decreases, due to which the excess of mosquitoes floating on the surface of water die due to sinking.
•When a ship enters in a see from a river it raise a bit because the density of saline water is higher.
Cohesive & Adhesive Force▪︎Force of attraction applied between molecules of same substance is called cohesive force while attractive force between molecules of different substance is called adhesive force. ▪︎A solid melts into liquid due to adhesive force. |
Capillarity
The phenomenon of rise or depression of liquids in a capillary
Bernoulli's Theorem
When an incompressible and non-viscous liquid (or gas) flows in streamlined motion from one place to another, then at every point of its path the total energy per unit volume (pressure energy) + kinetic energy + potential energy) is constant.
Venturimeter, Bunsen's Burner, Atomizer, filter pump, motion of aeroplane and Maynus effect are based upon the Bernoulli's theorem.
Simple Pendulum
•Simple pendulum is a heavy point mass suspended from a rigid support by means of an elastic inextensible string.
• The maximum time period of a simple pendulum is 84.6 min.
• A pendulum clock goes slow in summer and fast in winter.
• If a simple pendulum is suspended in a lift descending down with acceleration, then time period of pendulum will be increase. If lift is ascending, then time period of pendulum will be decrease. If a lift falling freely under gravity, then the time period of the pendulum is infinite.
Heat and Thermodynamics
• Heat is a form of energy which produces in us the sensation of warmness.
• Its unit are calorie, kilocalorie or joule.
• I calorie = 418 joule.
Temperature
• Temperature is the measurement of hotness or coldness of a body.
• When two bodies are placed in contact, heat always flows from a body at higher temperature to the body at lower temperature.
• An instrument used to measure the temperature of a body is called a thermometer.
• The normal temperature of a human body is 370C or 98.40F.
• -40 0 is the temperature at which Celsius and Fahrenheit thermometers read same.
• The clinical thermometer reads from 960F to 1100F.
• White roof keeps the house cooler in summer than black roof because white roof reflects more and absorbs less heat rays whereas black roof absorbs more and reflects less heat rays.
Thermal Expansion
•Thermal expansion is the increase in size on heating.
•A solid can undergo three types of expansions
(i) Linear expansion
(ii) Superficial expansion
(iii) Cubical expansio
• Telephone wires are kept loose to allow the wires for contraction in winter.• A gap is provided between two iron tracks of the railway track so that rails can easily expand during summer and do not bend. |
Latent Heat
Latent heat of fusion of ice is 80 cal/g.
Hot water burns are less severe than that steam burns because steam has high latent heat.
Evaporation
•It is the slow process of a conversion of liquid into its vapour even below its boiling temperature.
•The amount of water vapour in air is called humidityc.
•Relative humidity is measured by hygrometer.
•Relative humidity increases with the increase of temperature.
Transmission of Heat
•Transfer of heat from one place 'to other place is called transmission of heat.
•In solids, transmission of heat takes place by conduction process.
•In liquids and gases transmission of heat takes place by convection process. In room ventilaters are provided to escape the hot air by convection.
•Heat from the sun reaches the earth by radiation.
Light
•Light is a form of energy which is propagated as electromagnetic waves. Light is transverse wave.
•Speed of light is maximum in vacuum and air (3 x 106 m/s).
•Light takes 8 min 19 sec to reach from sun to earth.
Reflection of Light
•When a ray of light after inciding on a boundary separating two media comes ba.ck into the same media, then this phenomenon is called reflection of light.
Laws of Reflection
•The incident ray, reflected ray and normal ray to the reflecting surface at the incident point all lie in the same plane.
•The angle of reflection is equal to the angle of incidence.
Reflection from Plane Mirror
•The image is virtual laterally inverted.
•The size of image is equal to that of object.
•If an object moves towards a plane mirror with speed v, relative to the object the image moves towards with a speed 2v.
•To see his full image in a plane mirror, a person requires a mirror of at least half of his height.
•The number of images are formed by plane mirror n = ( 360°/θ - 1 )
Spherical Mirror
• Spherical mirror are of two types
(i) Concave mirror (ii) Convex mirror
•Image formed by a convex mirror is always virtual, erect and diminished.
Uses of Concave Mirror
(i) As a shaving glass. (ii) As a reflector for the head lights vehicle, search light. (iii) ,ln ophthalmoscope to examine eye, ear, nose by doctors. (iv) In solar cookers.
Uses of Convex Mirror
(i) As a rear view mirror in vehicle because it provides maximum rear field of view and image formed always erect. (ii) In sodium reflector lamp.
Refraction of Light
•The bending of the ray of light passing from one medium to other medium is called refraction. When a ray of light enters from one medium to other medium, its frequency and phase do not change but wavelength and velocity change.
• Due to refraction form earth's atmos- phere, the stars appear to twinkle.
Total Internal Reflection (TIR)
•If light is travelling from denser medium to rarer medium and the angle of incidence is more than the critical angle then the light is reflected back into the denser medium. This phenomenon is called total internal reflection.
•Sparkling of diamond, mirage and looming, shinning of air bubble in water and optical fibre are examples of total internal reflection.
•Refractive Index (μ) = speed of light in vaccum speed of light in the medium
Optical Fibre
• Works on the principle of TIR used for telecommunication and various medical purposes like endoscopy.
Lens
•Lens is generally of two types
(i) Convex lens (ii) Concave lens
•When lens is dipped in a liquid of higher refractive index the focal length increases and convex lens behaves as concave lens and vice-versa.
•An air bubble trapped in water or glass appears as convex but behaves as concave lens.
Dispersion of Light
•When a ray of white light is passed through a prism, it gets splitted into its constituent colours. This phenomenon is called dispersion of light.
•The different colours appeared in the spectrum area on the following order, violet, indigo, blue, green, yellow, orange and red (VIBGYOR).
•Wavelength of red colour is maximum and for violet colour is minimum.
•Red, green and blue are primary colours.
•Green and magenta, blue and yellow, red and cyan are complementary colours.
higher.
Green + Red + Blue = White Blue + Yellow = White Red + Cyan = White Green + Magenta = White Green + Red = Yellow Red + Blue =- Magenta Blue + Green = Cyan |
•Scattering of light is maximum in case of violet colour and minimum in case of red colour of light.
Human Eye
•Least distance of distinct vision is 25 cm.
•For point of normal eye is at infinity.
Defects of Eye
Myopia (Short sightedness)
A short-sighted eye can see only nearer objects. Distant objects are not seen clearly. This defect can be removed by using concave lens of suitable focal length.
Hypermetropia ( Long sightedness)
A long sighted eye can see distant objects clearly but nearer object are not clearly visible. This defect can be removed by using a convex lens.
Presbyopia
In this defect both near and far objects are not clearly visible. It can be removed by using bifocal lens.
Astigmatism
In this defect eye cannot see horizontal and vertical lines clearly. This defect cannot be removed by using cylindrical lenses.
Electricity and Magnetism
Charge
•Charge is the basic property associated with matter due to which it produces and experiences electrical and magnetic effects.
•Similar charges repel each other and opposite charges attract each other.
Conductor
Conductors are those materials which allow electricity to pass through themselves.
Metals like silver, iron, copper and earth acts like a conductor. Silver is the best conductor.
Insulator
Insulator are those materials which do not allow electricity to flow through themselves, wood, paper, mica, glass, ebonite are insulators.
Electric Current
• Electric current is defined as the rate of flow of charge or charge flowing per unit time interval. Its unit is Ampere, It is a scalar quantity.
Ohm's Law
The current flowing through a conductor is directly proportional to the potential difference across it.
I = V / R ,
where R is the resistance
•If a wire is stretched or doubled on itself its resistance will change, but its specific resistance will remain unaffected.
•On increasing the temperature of the metal, its resistance increases.
•On increasing the temperature of semiconductor its resistance decreases.
•On increasing the temperature of electrolytes, their resistance decreases.
•The reciprocal of resistivity of a conductor is called its conductivity. Its unit is mho m -1 .
Magnets
•Magnet is a piece of iron or other materials that can attract iron containing object and that points North and south when
•When a magnet is freely suspended, its one pole always directs towards the North. This pole is called North Pole. The
•Similar poles repel each other and dissimilar poles attract
Atomic and Nuclear Physics
Cathode Rays
Cathode rays, discovered by Sir William Crooke.
•These travel in straight lines.
•These produce fluorescence.
•These can penetrate through thin foils of metal.
•These are deflected by both electric and magnetic fields. These have velocity ranging 1-30th to 1-10th of the velocity of light.
Positive or Canal Rays
•These rays were discovered by Goldstein.
•The positive rays consists of positively charged particles.
•These rays travel in straight line.
•These rays are deflected by electric and magnetic fields. These rays are capable of producing physical and chemical changes.
•These rays can produce ionisation in gases.
X-Rays
•X-rays are electromagnetic waves with wavelength range 0 1 A—IOO A. X-rays were discovered by Roentgen.
•X- rays travel in straight line. These show reflection, refraction, interference, diffraction and polarization and do deflected by electric and magnetic fields.
•Long exposers of X-rays is injurious for human body.
•X-rays shows photoelectric effect.
Uses of X-rays
•In medical sciences X-rays are used in surgery for the detection of fractures, diseased organs, foreign matter like bullet, stones etc. They are used in treatment of cancer and in skin diseases.
•Engineering X-rays are used in detecting faults, cracks, flaws and gas pockets in the finished metal products and in heavy metal sheets.
•Scientific work X-rays are used in studying crystal structure and complex molecules.
•In custom department X-rays are used in custom department for detection of banned materials kept hidden.
Radioactivity
•Radioactivity was discovered by Ilenry Becquerel, Madame Curie and Pierre Curie for which they jointly win Nobel Prize.
•The nucleus having protons 83 or more are unstable, They emit α, βand γ particles and became stable. The elements of such nucleus are called radioactive elements and the phenomenon of emission of α, βand γ particles is called radioactivity.
•Robert Pierre and his wife Madame Curie discovered a new radioactive element radium.
•The end product of all natural radioactive elements after emission of radioactive rays is lead.
•With the emission an α-particle, atomic number is decreased by 2 and mass number is decreased by 4.
With the emission of a β -particle atomic number is increased by 1 and mass number does not change.
Nuclear Fission
•The nuclear reaction in which a heavy nucleus splits into two nuclei of nearly equal mass is nuclear fission.
92U235 +0 n1 ➡️ 56 Ba141 + 36Kr92 + 3 0n1+ energy
•Nuclear fission was first demonstrated by Strassman and O Hahn.
•Atom Bomb is based on nuclear fission. U 235 and Pu 239 are used as fissionable material.
Nuclear Fusion
•When two or more light nuclei combined together to form a heavier nucleus is nuclear fusion.
•For the nuclear fusion, a temperature of the order of 10 8 Kis required.
•Hydrogen Bomb was made by the American Scientist in 1952. This is based on nuclear fusion. It is 1000 times more powerful than atom bomb.
Nuclear Reactor or Atomic Pile
•Nuclear reactor is an arrangement in which controlled nuclear fission reaction takes place.
•First nuclear reactor was established in Chicago University under the supervision of Prof Fermi.
Uses of Nuclear Reactor
•To produce electrical energy avom the energy released during fission.
•To produce different isotopes which can be used medical, physical and agricultural science