| Motion: Movement of any object from one position to another position with respect to the observer is called as Motion. Motion Along a Straight Line: When an object moves along a straight line, the motion of the object is called rectilinear motion. For example; motion of a car on highway. Vectors and Scalar Quantities: - Vector is a quantity which has both magnitude and direction. For example, Force, position, etc.
- Scalar is a quantity with which direction is not associated. For example, Mass, temperature, time, etc.
Distance: - Length of path covered by a moving an object in the given time irrespective of the direction
is called distance. - It is a scalar quantity.
- Its SI unit is metre(m).
Displacement: - The shortest distance measured from initial to the final position of an object is known as the displacement.
- It is a vector quantity.
Uniform Motion:
- When an object covers equal distances in equal intervals of time, it is said to be in uniform motion.
Non-Uniform Motion: - When an object covers unequal distances in equal intervals of time, it is said to be in non-uniform motion.
Speed (s): - The distance travelled by an object in unit time is referred to as speed.
- It is represented as:
 - Its SI unit is metre/ second (m/s).
- It is a scalar quantity.
- Average speed: For non-uniform motion, the average speed of an object is obtained by dividing the total distance travelled by an object by the total time taken.
 Velocity (v): - Speed of an object in a particular direction is named as velocity, i.e., it is the displacement of body in unit time.
- It is represented as:
- It is a vector quantity.
- Average velocity: It is given by the arithmetic mean of initial velocity and final velocity for a given period of time.
Acceleration (a): - The rate of change of velocity is termed as acceleration.
- It is represented as:
 - Its SI unit is metre/seccond2 (m/s2).
- It is a vector quantity.
- The acceleration is taken to be positive if it is in the direction of velocity and negative when it is opposite to the direction of velocity.
- Negative acceleration is also named as retardation or deacceleration.
- An object moving on a circular path though with uniform speed, is always said to be accelerated as it changes its direction every moment.
- Uniform acceleration: When velocity of body changes by equal amounts in equal time intervals, acceleration is said to be uniform. For example: Motion of a freely falling ball.
- Non - uniform acceleration: When velocity of body changes by unequal amounts in equal intervals if time, acceleration is said to be non - uniform. For example: Motion of car.
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