# Describing Motion #### Rest

A body is said to be in the state of Rest if it doesn’t change it’s position with respect to time and surrounding.
For example: Bottle kept on a table, A table lying in a corner, Passengers sitting in a bus, train, aeroplane etc.

#### Motion

A body is said to be in the state of Motion if it change it’s position continuously with respect to time and surroundings.
For example: A fan moving, Flying a kite, Moving of a car, Boy on a swing etc.

#### Scalar Quantity

The quantity that deals with the magnitude only (numeric).
For Example: Distance, Speed, Work etc

#### Vector Quantity

The quantity that deals with the magnitude as well as direction.
For Example: Displacement, Velocity, Acceleration etc

#### Distance

It is defined as the actual length of the path covered by the body.

• The S.I. unit of distance is metre (m)
• It is a scalar quantity
• It can never be zero or negative

#### It is defined as the shortest distance between the initial point and the final point.

• The S.I. unit of distance is metre (m)
• It is a vector quantity
• It can be zero or negative

#### Uniform Motion

A body is said to be in uniform motion if it covers equal distances in equal intervals of time.

#### Non-Uniform Motion

A body is said to be in non-uniform motion if it covers unequal distances in equal intervals of time.

#### Speed

Speed is defined as distance traveled by the object in unit time i.e. Speed = Distance/Time.

• It is denoted as V i.e. V = S/T.
• It is a Scalar Quantity
• The S.I. unit of speed is m/s.

#### Average Speed

The average speed of an object is obtained by dividing the total distance traveled by the total time taken i.e. Average Speed = Total Distance/Total Time Taken.

#### Velocity

Velocity is the speed of an object moving in a definite direction. The velocity of an object can be uniform or variable.

• Velocity = Speed + Direction
• V = Displacement/Time
• The S.I. unit of velocity is m/s.
• It is a Vector Quantity

#### Average Velocity

Average Velocity is given by the arthematic mean of initial velocity and final velocity for a given period of time i.e. Average Velocity = Initial

• Velocity + Final Velocity/2
• Mathematically : Average Velocity = U+V/2
• Average Velocity = Total Displacement / Total Time Taken

#### Types of Acceleration

• Positive Acceleration
When final velocity is more than initial velocity in that case acceleration would be positive.
• Negative Acceleration
When initial velocity is more than final velocity in that case acceleration would be negative.
• Zero Acceleration
When a body moves with a constant velocity i.r. V=U in that case acceleration would be zero.

#### Accelerated Motion

• Uniformly Accelerated Motion
An object travels in a straight line and its velocity increases or decreases by equal amount in equal amount in equal intervals of time, then the acceleration is said to be in uniform.
For Example: The motion of a freely body falling.
• Non-Uniform Accelerated Motion
An object can travel with non-uniform acceleration if it’s velocity changes at a non-uniform rate.
For Example: If a car travels along a straight road increases it’s speed by unequal amounts in equal intervals of time, then the car is said to be moving in non-uniform accelerated motion. 