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General Science-Physics Mechanics

Matter:

Matter consists of something which has weight, occupies space and which can affect our senses.

Molecule:

Molecule Matter is made of molecule. A molecule is the smallest particle of a substance which can exist in a free state and possesses the properties of that substance.

Atom:

Atom is the smallest particle of an element, capable of taking part in a chemical reaction.

Mass Weight:

Mass Weight is the quantity of matter contained in a body. Force with which a body is attracted towards each.

Difference between Mass and Weight:

The weight differs at different places in accordance with the variation in gravity(g) while the mass always remains the same.
Mass is measured in Kilograms or pounds, while weight is measured in dynes and poundals. Unit of mass is Kilogramme.

Density Mass per unit volume.

Specific Gravity:

The ratio of the mass of a given volume of the substance to the mass of an equal volume or water.

Motion: Change of position of a body with respect to its surroundings.

Speed: Is the rate of motion and is a scalar quantity, ie., possesses magnitude only.

Velocity: Is the rate of motion in a particular direction. It is vector quantity, ie., possesses both magnitude and direction.

Uniform Speed: When a body traverses equal distance in equal intervals of time, however small the intervals of time may be, it is said to have uniform speed.

Acceleration: Is the rate of increase of velocity.

Retardation: Is the rate of decrease of velocity.

Force: Is a push or pull which changes or tends to change, destroys or tends to destroy the acceleration in a moving body.

Newton's First Law of Motion:

It states that a body continues in the state of rest or of uniform motion in a straight line unless it is impelled by an external force to change that state.

Newton's Second Law of Motion:

It states that the acceleration of an object is dependent upon two variables, the net force acting upon the object and the mass of the object.

Newton's Third Law of Motion:

It states that action and reaction are equal and opposite.

Centripetal and Centrifugal Force:

When a small piece of stone is tied to one end of the string and then whirled, one has to pull the string Force inwards. This pull acting on stone is called the centripetal force. An equal and opposite force is exerted by the stone on the hand which is called centrifugal forces.

Gravity: Force with which a body is attracted towards earth.

Law of Gravitation:

Every particle in this universe attracts every other particle with a force which is directly proportional to the product  of distances between them.

Relative Velocity: Velocity of one body in relation to another.

Impulse: Is the change of momentum produced in a body and is equal to the product of force and time.

Work: When the point of application of the force moves work is said to be done.

Erg: Is the unit of work and is the amount of work done when a force of one dyne moves a body through 1cm. In the direction of the force. Erg is the C.G.S. unit of work.

Power: Rate of doing work is called power.

Horse Power: Is the unit of power, i.e., rising 33,000 lb of weight through one foot high in one minute.

H.P=550 foot pounds of work done in 1 sec
1 H.P=746 watts
1 watt 107 ergs/sec

Watt: Is the unit of power in C.G.S. system

Energy: Capacity to do work is called energy.

Potential Energy: Energy due to its position

Kinetic Energy: Energy due to motion.

Equilibrium: If the force acting on a body produces no change in its state of rest ormotion, the body is said to be in equilibrium.

Lever: It is a straight bar which is capable of rotation around a fixed point called fulcrum.

Surface Tension: The force of tension on account of their intermolecular forces on the surface of a liquid is called surface tension.

Archimedes: When a body is immersed in a liquid, it experiences an upward Principle thrust. the upward thrust of loss of weight is equal to the liquid displaced.


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General Science Heat, Light and Magnetism for upsc ssc cgl preparation

General Science Heat, Light and Magnetism for upsc ssc cgl preparation


Heat:

Calorie: Is the amount of heat required to raise the temperature of 1 kg. of water to 1 degree centigrade.

Effects of Heat:

• Increase temperature and volume. 
•  Changes state.
• Brings about chemical action.
• Changes physical properties.

Temperature: Is the degree of hotness in a body.

Latent Heat: Is the heat which is spent in changing the state of a body without raising its temperature.

Evaporation: Change of state from liquid to vapor. Cooling is caused by evaporation.

Transference of Heat: Heat can be transferred in three ways.

• Conduction: The process in which heat is transferred from particle.
• Convection: The transfer of heat from on part of the body to another by the actual motion of the heated particle of a gas or liquid.
• Radiation: The process by which heat is transferred from one point to another without heating the medium.

Relegation: The process by which are joined two or more blocks of the ice by placing one above the other. It is due to the pressure that ice below melts and water again solidifies to form one mass.

Freezing Mixture: Such mixtures by means of which we can produce low temperature.

Ex:- Common salt mixed with ice.

Air Conditioning: The process of regulating the human temperature and circulation of air in a public building, office or factory.

Light:

Colour Blindness: When a person cannot distinguish between different colours (especially between green and red).

Reflection: A ray of light falling on a mirror is sent back by the law of reflection.

Laws of Reflection:

• The reflected ray, the incident ray and the normal at a point lie in the same plane.
• The angle of incidence is equal to the angle of reflection.

Refraction: When a ray of light is incident obliquely on a surface of separation between two media, part of it goes into the second medium along a path different from the direction of the incident beam. This phenomenon is called refraction.

Law of Refraction:

• The incident ray, the refracted ray and the normal at a point lie in the same plane.
• The ratio of the sine of the angle of incidence is constant, is called the refractive index of the medium.

Mirage: Is an optical illusion due to total internal reflection.

Astigmatism: One can see vertical lines clearly but not the horizontal ones or vice versa remedied by using cylindrical glasses.

Myopia(short-sightedness): A myopic person can see nearer objects distinctly but not the distant ones. Remedy: Use of concave lens.

Hypermetropia(long-sightedness): A person can see distant objects distinctly but not near ones.

Remedy: Use of convex lens.

Magnetism:

Magnet: Is a substance having a property of attracting pieces of iron, cobalt, nickel, etc. A magnet when freely suspended points towards North and South.

Lodestone: Is a compound of iron and oxygen. It attracts pieces of iron, cobalt, nickel, etc. When suspended points in the North and South directions. It is natural magnet.

Artificial Magnet: Substance that has been imparted the properties of a magnet by artificial means. This involves rubbing a magnet over a piece of steel again and again till magnetized.

Nuclear Physics:

Nuclear Physics has grown into one of the most significant branches of science, leading as it does to modern theories of atomic structure to nuclear weapons and to the production of radio-isotopes for use in industry and medicine. It began with the study of radioactivity discovered by the French Physicist Henri Bacquerel in 1896 when he found that invisible radiation from pitchblende- a mineral containing uranium could fog a photographic plate.



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