# Motion

## Scalar Quantities

Physical quantities which have magnitude only and direction are called scalar quantities.
Example : Mass, speed, volume, work, time, power, energy etc.

## Vector Quantities

Physical quantities which have magnitude and director both and obey triangle law are called vector quantities.
Example : Displacement, velocity, acceleration, force, momentum, torque etc

Electric current, though has a direction, is a scalar quantity’ because it does not obey triangle law.

## Distance

Distance is the length of actual path covered by a moving object in a given time interval.

## Displacement

Shortest distance covered by a body in a definite direction is called displacement.

Distance is a scalar quantity where displacement is a vector quantity both having the same unit (metre)
Displacement may be positive, negative or zero whereas distance is always positive. In general, magnitude of displacement < = distance.

## Speed

Distance travelled by the moving object in unit time interval is called
SI unit of distance is metre/second (m/s).

## Velocity

Velocity of a moving object is defined as the displacement of the object in unit time interval
It s a vector quantity and its SI unit is meter/second.

## Acceleration

Acceleration of an object is defined as the rate of change of velocity of the object
It s a vector quantity and its SI unit is meter/second2 (m/s2).
If velocity decreases with time then acceleration is negative and is called retardation.

## circular Motion

If an object describes a circular path (circle) its motion is called circular motion. 1f the object moves with uniform speed, its motion is uniform circular motion.
Uniform circular motion is an accelerated motion because the direction of velocity changes continuously, though the magnitude of velocity i.e. speed of the body remains unchanged.

## Angular Velocity

The angle subtended by the line joining the object from the origin of circle in unit time interval is called angular velocity.