KINEMATICS NOTES

Kinematics Physics Notes

DEFINITION
"It is the branch of Physics which deals with description of motion without reference to any opposing or external force".


MOTION
"When a body changes its position with respect to its surrounding so the body is said to be in the state of motion".

TYPES OF MOTION
There are three types of motion:
          1) Linear or Translatory motion

          2) Rotatory motion

          3) Vibratory motion


1. Linear or Translatory Motion
If a body moves in a straight path so the body is to be in Linear motion or Translatory motion.

Example : A bus is moving on the road, A person is running on the ground.


2. Rotatory Motion
If a body spins or rotates from the fixed point ,so the body is to be in Rotatory motion.

Example : The blades of a moving fan, The wheel of a moving car.


3. Vibratory Motion
To and fro motion about the mean point so the body is to be in Vibratory motion.

Example: Motion of a spring.





REST
"When a body does not change its position with respect to its surrounding so the body is said to be in the state of rest".

Example: A book is laying on the table,A person is standing on floor,A tree in the garden.





SPEED
"The distance covered by a body in a unit time is called speed."

                               OR

"The rate of change of distance is called speed."


FORMULA
Speed = Distance/Time
       V = S/t


UNIT
The S.I unit of speed = Meter/second.
                                = m/s

Kinds Of Speed
1. Uniform Speed :
          If a body covers an equal distance in equal interval of time so the body is said to be in uniform speed.

2. Variable speed :
          If a body does not cover an equal distance in equal inteval of time so the body is said to be in variable speed.




VELOCITY
"The distance covered by a body in a unit time in a particular direction is called velocity."

                                       OR

"The rate of change of displacement is called speed."

                                       OR

"Speed in a definite direction is called velocity."


FORMULA
Velocity = Displacment/Time
          V = S/t


UNIT
The S.I unit of Velocity = Meter/second.
                                  =m/s


Kinds Of Velocity
1. Uniform Velocity : 
             If a body covers an equal distance in equal interval of time in a Constant direction so the body is said to be in uniform Velocity.

2. Variable Velocity :
             If a body does not cover an equal distance in equal interval of time in a particular direction so the body is said to be in variable velocity.


ACCELERATION
"The rate of change of velocity is called acceleration."

                                 OR

"Acceleration depends upon the velocity if the velocity continously increases or decreases the accelerattion will be produced."


1) Positive Acceleration :
          If the velocity continously increases then the acceleration will be positive.

2) Negative acceleration :
          If the velocity continously decreases then the acceleration will be negative.


FORMULA
Acceleration = change of velocity/Time
                a = (Vf-Vi)/t


UNIT
The S.I unit of Velocity = Meter/second+square
                                  =m/S2


EQUATION OF MOTION
The relationship of initial velocity, final velocity, acceleration, time,and linear distance.


FIRST EQUATION OF MOTION
suppose an object moves with initial velocity "Vi" in a time "t" and covers a distance "S" in an acceleration "a" and the final velocity of an object becomes "Vf"

According to the defination of the acceleration "The rate of change of velocity is called acceleration"

i.e. Acceleration = Change of velocity/time

=> a = Vf - Vi/t


DERIVATION

a = Vf - Vi/t

at = Vf - Vi

or Vf = Vi + at


SECOND EQUATION OF MOTION

According to the definition of the acceleration "The rate of change of velocity is called acceleration".

i.e. Acceleration = Change of velocity/time

=> a = Vf - Vi/t

at = Vf - Vi

or Vf = Vi + at -------------(1)

Substituting the average velocity:

Vav = (Vi + Vf)/2 -----------(2)

The distance covered by the body in a unit:

S = Vav/t

Putting the value of Vav from equation 2:

S = [(Vi + Vf)/2] * t

Putting the value of Vf from equation 1:

S = [(Vi + Vi + at)/2] * t

S = [(2Vi + at)/2] * t

S = (Vi + at/2} * t

S = (Vit + 1/2at2) {Here 2 is the square of the time "t". Dont write this sentence in the examination}


THIRD EQUATION OF MOTION

According to the definition of the acceleration "The rate of change of velocity is called acceleration".

Acceleration = Change of velocity/time

=> a = (Vf - Vi)/t

=> at = Vf - Vi

or t = (Vf - Vi)/a -------------(1)

Subsituting the average velocity:

Vav = (Vi + Vf)/2 -----------(2)

We know that:

Vav = S/t

=> S = Vav * t

Putting the value of Vav from equation 2 and value of t from eq 1:

S = [(Vi + Vf)/2] * [(Vf-Vi)/a]

S = Vi2 - Vf2/2a since {(a+b) (a-b) = a2 - b2}

or 2as = Vf2 - Vi2