Equation of Motion
v Rest and Motion
When do we say that a body is at
rest and when do we say that it is in motion?
If a body does not change its
position at time passes it is at rest. If a body changes its position with
time, it is said to be moving.
v Position
To locate an object means to find
its position relative to some reference point, often the origin of an axis such
as the x – axis.
X = 5m, It is 5m in the +ve
direction from the origin.
v Displacement
Length of the straight line joining
the source to the destination or in other words the length of the shortest
path.
A change from one position X1
to another position X2 is called a displacement 
where
–
If the particle returns to the
original position, the displacement for the full 4rip is zero. Displacement
involves only the original and final positions.
v Distance
Length
of the actual path taken to go from source to destination.
v Velocity
The rate of the change of
displacement of a moving body is called the velocity of a body. Velocity is a
vector quantity, SI unit m/s.
v Instantaneous Velocity
When a particle moves with variable
velocity, then the velocity at a certain moment is called the instantaneous
velocity.
v Uniform Velocity
When the moving particle covers
equal distances in equal intervals of time in a fixed direction, then its
velocity called uniform velocity.
v Speed
The distance travelled by a moving
body per unit time is called the speed of the body. It is a scalar quantity.
Speed is the magnitude of velocity.
v Acceleration
The rate of change of velocity of a
moving particle with respect to time is called the acceleration. It is a vector
quantity.
If the rate of change of velocity is negative, it I called retardation.
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