The branch of physics which deals with the study of motion of material objects is called mechanics.

Mechanics is classified into kinematics and statics.

Kinematics: study of motion of objects

Statics: study ofobjects at rest

Rest and Motion:

          If the position of thepointor body does not change with the time, it is said to be in rest.

          If the position changes with time, it is said to be in motion.

Distance and displacement

          The total length covered y a body is called distance.

          Thenet change in position of the body in a certain time interval, with respect to the fixed point is called its displacement.


  • Speed is the quantity used to say whether the motion is slow or fast, Speed is the distance travelled in one second (or) rate of distance traveled.       

           Speed is measured in m/s (or) ms-1


  • Velocity is the Displacement made in one second (or) rate of change of displacement.
  • Rate of change means, change per second.




Uniform Velocity

  • Equal displacement covered by a body in equal intervals of time is known as uniform velocity.

Rate of Change of Velocity

  • Acceleration is the change in velocity of an object per second or rate of change of velocity.                                           Changeinvelocity



  • If the velocity of the body decreases with time, the accelerations is negative (retardation), and the motions called decelerated motion.

Graphical Representation of Motion

Distance – time graph

Equation for velocity at a time


                   s=ut+1/2 at2…….(II)


Acceleration due to gravity

  • The declaration or acceleration due to the gravitational force of earth I known as
  • The average value of ‘g’ is 9.8 m/s2.

Uniform Circular Motion

  • In uniform circular motion, the magnitude of the velocity is constant at all points and the direction of the velocity changes continuously.
  • One radian is the angle subtended by an arc of a circle of length equal to its radius at the center of the circle.

Angular displacement

  • The angle covered by the line joining the body and the centre of the circles (radius vector). It is measured in radian.

Angular velocity

                   Angular velocity =                                           

 The unit of angular velocity?

It is radian/second.

Relational between linear and angular velocity

  • Linear velocity=Radius of the circle x Angular velocity



  • Issac Asimov is called as father of Robot.
  • It is he who named the machine as Robot (derived from Philippines language)
  • Robot is a human machine.
  • Robots are run by heavy batteries.
  • Robots brain is nothing but an electronic chip.
  • The first electric cell was developed by an Italian scientist Luigi Galvani and then improved by Alessandro Volta.
  • Tamil Nadu is the No.1 state in India with the highest wind power generating capacity of about 5,000 MW.
  • Most wind farms are in Thoothukudi, Kanyakumari and Thirunelveli Districts of Tamil Nadu.
  • An electric cell is a device which converts chemical energy into electric energy.
  • The cell is a source of electric current.
  • Electric current is the flow of electrons or charge.
  • Electric eel is an electric fish.
  • It is capable of generating powerful electric shocks for hunting its prey and for self defense.
  • Electric eel lives in the fresh water of the Amazon and Orinoco river basins in South America.
  • The sun gives us 3.8 x 1026 joule of heat energy per second.
  • This energy is produced by nuclear fusion.
  • The sun is the Prime source of heat energy without which life would be impossible on the earth.
  • Now a days solar energy is used in solar cookers and solar heaters.
  • Joule is the unit used to measure energy.
  • Celsius and Fahrenheit are valid terms used in the measurement of temperature.
  • Thermometers have two different scales to measure temperature.

a)Centigrade or Celsius scale.

b)Fahrenheit scale

  • The SI unit of temperature is Kelvin.
  • Most thermometers use mercury because
  • It is opaque and shiny.
  • Does not stick to glass.
  • It is a good conductor of heat.
  • It shows large expansion for small temperature changes.
  • It expands uniformly.
  • In some thermometers ALCOHOL is used.
  • The normal body temperature is (36.90F)
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