Speed, Velocity & Acceleration – SSC

Speed
The distance covered by a moving body in a unit time interval is called its speed.

Velocity
The time rate of change of displacement of a body is called its velocity.

An object is said to be moving with uniform velocity if it undergoes equal displacements in equal intervals
of time.
An object is said to be moving with non-uniform or variable velocity if it undergoes unequal displacement
in equal intervals of time.

Acceleration

 When a body travels equal distances with speed
and
, then average speed is the harmonic mean of
the two speeds.

 When a body travels for equal times with speeds
and
, then average speed is the arithmetic mean of
the two speeds.

Velocity
The time rate of change of displacement of a body is called its velocity.

An object is said to be moving with uniform velocity if it undergoes equal displacements in equal intervals of time.
An object is said to be moving with non-uniform or variable velocity if it undergoes unequal displacement in equal intervals of time.

Acceleration
The time rate of change of velocity of a body is called its acceleration.

 It is a vector quantity and its SI unit is

Acceleration at an instant of time is known as instantaneous acceleration.
When the velocity of a body increases with time, then its acceleration is positive and if velocity decreases with time, then its acceleration is negative called
deceleration or retardation.
If acceleration does not change with time, it is said to be constant acceleration.