**Acceleration**

When the velocity of an object changes it is said to be accelerating. Acceleration is the rate of change of velocity with time.

Acceleration “a”, is equal to the difference between the initial and final velocities divided by the time, it took for the velocity to change from V

Acceleration is due to the change in velocity. Since velocity have a speed and a direction, there are only two ways for you to accelerate: change your speed or change your direction.

a change in the direction of motion results in acceleration even if the moving object neither speed up nor slowed down. Because acceleration depends on the change in velocity ( speed or direction change).So, we can say that a body moving in a circle with uniform velocity has acceleration due to change in its direction at every instant

Acceleration does not relate to the high speed or low speed of the body. A body moving with high speed can have minimum or zero acceleration ( An aeroplane moving with uniform velocity ) and a body moving with very low speed can have very high acceleration ( A runner starting its race ).

**Positive Acceleration**

If the velocity of a body is increasing, the acceleration will be positive.

A car starting from rest and reach upto 80 Km/h.

**Negative Acceleration / Deceleration.**

If the velocity of an object slows down, this is called deceleration or negative acceleration.

A car is moving with 80Km /h and after applying break, its speed become 10Km/h. The direction of the acceleration is in the opposite direction of the movement of the object.

**Uniform acceleration.**

If the velocity of a body is increasing or decreasing with a constant value, the acceleration will be uniform.

A car starting from rest and after 5 second its velocity become 15 m/s2, after 10 second its velocity become 30 m/s2, after 15 second its velocity become 45 m/s2.

**Variable acceleration.**

If the velocity of a body is increasing or decreasing with a variable value, the acceleration will be variable.

A car starting from rest and after 5 second its velocity become 20 m/s2, after 10 second its velocity become 30 m/s2, after 15 second its velocity become 55 m/s2.