KINEMATICS..PHYSICS..PART 1

Rest and Motion are relative terms, nobody can exist in a state of absolute rest or of
absolute motion.

Speed:- It is rate of change of distance covered by the body with respect to time.
Speed = Distance travelled /time taken
Speed is a scalar quantity
S.I. unit is m /s
dimensional formula is[M
0
L
1
T
-1
]

*Uniform Speed:-  If an object covers equal distances in equal intervals of time than the
speed of the moving object is called uniform speed.
In this type of motion, position –time
graph is always a straight line.

*Instantaneous speed:-The speed of an object at any particular instant of time is called
instantaneous speed. In this measurement, the time ∆t→0.
When a body is moving with uniform speed its instantaneous speed = Average speed =
uniform speed.

*Velocity:- It is defined as the displacement covered by an object per unit time.
                                             Velocity =Displacement /Time
                                               Velocity is a vector quantity
                                             SI unit is m /s


Its  dimensional formula  is (see speed)

difference between speed & velocity :
1.Speed is scalar but velocity is vector quantity.
2.speed may be +veor zero where as velocity may be zero,+ve or -ve.

*Acceleration:-  The rate of change of velocity of an object  with respect to time  is called 

its acceleration.
Acceleration = Change in velocity /time taken
unit-m/s(2)
It may be positive ,negative or zero.
*Positive Acceleration:- If the velocity of an object increases with time , its acceleration is 
positive .
*Negative Acceleration :-If the velocity of an object decreases with time ,  its acceleration 
is negative . The negative acceleration is also called retardation or deacceleration.