MECHANICS

• It is concerned with the study of motion of objects. Motion is the change in the position of the body with a point, during a certain period.
• Motion is of two types- linear (translational) and spin (rational). The movement of the car on the road is a linear motion, while a spinning wheel on an axis is a spin motion.
• The speed of a moving body is the ability to cover a distance in a unit time.
• The velocity is the rate of change of displacement, or the distance covered by object in specific direction in unit time interval.
• Acceleration is the change of velocity.
• Angular velocity is the rate of change of angle of a rigid body rotating about an axis.

Force

• This word denotes a push or a pull. A force produces change in a body’s state of rest or of uniform motion in a straight line.
• There are different kinds of forces such as tension, friction, gravitation etc.
• Gravitational force is the force, which pulls everything towards the earth. The gravitational force exists between all bodies. It is gravitational force that holds the moon in its orbit round the earth and the earth in its orbit round the sun. Newton’s law of universal gravitation states that every particle in the universe attracts every other particle with a force.
• Centripetal force is a type of force, directed towards the centre, and thence called as the centripetal force, and is necessary to produce continuous change of direction in a circular motion.
• When a stone tied at one end of a string and circled around a hand, the pull in the string provides the centripetal force.
• Centripetal force is a force, which act upon a body revolving in a circle. Centrifugal force equals and neutralizes the centripetal, or its acts outwards.
• Weight is the force with which a body is attracted towards the centre of the earth. Weight is obtained by multiplying the mass of the body with acceleration due to gravity (g). Mass of the body remains constant where as weight will vary from place to place on the earth and elsewhere in the universe. This variation in weight is due to:
• (i) The shape of the earth, and
• (ii) The rotation of the earth about its axis, the centrifugal force in zero exactly at the poles and maximum at the equator.
• Friction is a force, which opposes the relative motion of two surfaces, which are in the contact. It plays an important role in our day-to-day experiences like walking made easier, roll down of cars, etc on the roads.

Newton’s laws of motion

• The motion of physical bodies obeys three basic laws, which were formulated by Sir Issac Newton.
• Newton’s First Law (Law in inertia), states that every body continues in uniform motion in a straight line unless compelled by an external force to act otherwise. The several phenomena are explained using the principle like if a fast moving bus stop suddenly, passengers bend forward, removal of a dust from a carpet, running fast before long jump, a bullet fired from a gun, and forms a hole in a windowpane etc.
• According to the Newton’s second law, the rate of change of momentum of a body is proportional to the unbalanced forces acting on it and is inversely proportional to its mass. The second laws explains- why is a car stops when breaks are applied, and why is a glass bottle dropped in sand would not break than a hard floor.
• The Third law of motions states that to every action there is an equal and opposite reaction. If a body A exerts a force on a body B, then B exerts an equal and opposite force on A along the same line of action. As we fire a gun, the forward thrust of the projectile is matched by the backward thrust, or the rockets do work on same principle.

FLOTATION AND ARCHIMEDES PRINCIPLE
Buoyancy 

• It is the force acting upward on an immersed solid, which is a reaction of the displaced fluid to the immersion.
• Archimedes principle states that when a solid body is partially or fully immersed in fluid, and it displaces fluid to an equal volume weight of the body.
• The two forces act on a body, when it is immersed.
  i)     Weight in the air of the body acting downward on the immersed body, and
  ii)    The buoyancy of the displaced water acting upward on the in body.
• The magnitude of the two forces determines whether a body will float in the fluid or not.
• Centre of buoyancy (CB) is the centre of gravity of the volume of the fluid displaced by the immersed body.

Application of Archimedes’ principles

• Hydrometer, measures the absolute density of the relative density of liquids.
• Submarines are made to sink of float by controlling the amount of water in their ballast tanks.
• Air ship & balloons float in the air, due to Archimedes principal.

THERMODYNAMICS

• Field of physics that describes and correlates the physical properties of macroscopic systems of matter and energy. The principles of thermodynamics are of fundamental importance to all branches of science and engineering

Zeroth Law of Thermodynamics 

• states that when each of two systems is in equilibrium with a third, the first two systems must be in equilibrium with each other. This shared property of equilibrium is the temperature.

First Law of Thermodynamics

• The first law of thermodynamics gives a precise definition of heat, another commonly used concept.
• The first law, then, is a law of energy conservation. It states that, because energy cannot be created or destroyed—setting aside the later ramifications of the equivalence of mass and energy the amount of heat transferred into a system plus the amount of work done on the system must result in a corresponding increase of internal energy in the system. Heat and work are mechanisms by which systems exchange energy with one another.

Second Law of Thermodynamics

• The second law of thermodynamics gives a precise definition of a property called entropy. Entropy can be thought of as a measure of how close a system is to equilibrium; it can also be thought of as a measure of the disorder in the system. The law states that the entropy—that is, the disorder—of an isolated system can never decrease. Thus, when an isolated system achieves a configuration of maximum entropy, it can no longer undergo change: It has reached equilibrium. Nature, then, seems to “prefer” disorder or chaos. It can be shown that the second law stipulates that, in the absence of work, heat cannot be transferred from a region at a lower temperature to one at a higher temperature.

Third Law of Thermodynamics

• The second law suggests the existence of an absolute temperature scale that includes an absolute zero of temperature. The third law of thermodynamics states that absolute zero cannot be attained by any procedure in a finite number of steps. Absolute zero can be approached arbitrarily closely, but it can never be reached.

HEAT  

• It is a form of energy, which is related to the temperature difference between bodies. The greater the internal energy of a substance, the hotter it will be.
• Calorie-The quantity of heat necessary to raise I gram of water through 1C.
• Calorimeter-A device is used to measure the quantity of heat involved in a system.

Temperature Scales

• There are three main temperature scales, Fahrenheit , Celsius, and Kelvin all named after the scientists who originated the scales. In certain contexts, one scale might be more appropriate to use than another scale and there are linear formulas that allow you to convert from one system to another.
• To convert from Celsius to Fahrenheit, the equation is
• F = (9/5)C + 32,
• where F stands for the temperature measured in Fahrenheit and C stands for the temperature measured in Celsius..
• To convert from Celsius to Kelvin, the equation is
• K = 273+C
• where K stands for the temperature measured in Kelvin and C stands for the temperature measured in Celsius.
• To convert from Kelvin to Fahrenheit, we need to combine the equation
• F = (9/5)C+32,

Transmission of heat 

• There are three ways by which transmission of heat occurs.
• Conduction- It is transfer of energy arising from the temperature difference between adjacent parts of a body.
• Convection- Heat is carried from one place to another by the actual movement of liquids and gases. When water in a beaker is heated up, the convection currents get established, thus ensuring the warming up of the water.Other phenomena associated are ventilation in room, wind systems and ocean currents.
• Radiation- The heat energy is transferred in the form of radiation energy. For this transfer no material medium is required.The heat of sun reaches the earth through atmosphere by radiation only.

Changes of state

• An important effect of heat is change of state.
• There are three states or phases in which matter can exist solid, liquid and gas. A fourth state has been named as plasma, which exists at very high temperature in the ionic form
• Evaporation is the escape of molecules from liquid surface in the form of gas or vapour.In the pressure cooker, pressure inside cooker is increased by not allowing the vapour to escape and thus boiling point is raised to make cooking easier.
• Condensation- is a change from vapour to liquids state. The temperature at which vapour condenses into liquid is known as a dew point.
• Sublimation- Some solid substances change into vapour state from solid state without going through liquid state. Ex. iodine crystals, camphor para-dl-chloro benzene, dry ice etc.