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Acceleration (a) is defined as the rate of change of velocity of an object with time. Here velocity is the rate with an object moves from one place to another. Velocity is a vector quantity, which means it has both a magnitude, called speed, and a direction. This makes acceleration also a vector quantity.

The SI unit for acceleration is metre per second squared (m s-2).

This physics term is described by Newton’s Second Law of motion states that the force on an object equals the mass times the acceleration. This is written in the following equation:

Force = mass * acceleration
F = ma

We can use this formula to also figure out the acceleration if we know the mass and force on an object. This formula is: 

acceleration = Force/mass
a = F/m

Any change in the velocity of an object results in acceleration. Increasing speed is called acceleration and decreasing speed is called deceleration or changing direction. So acceleration occurs anytime when object’s speed increases, decreases or changes direction.

Types of acceleration:

  1. Free fall case : During free fall, gravity applies a constant force on the object causing a constant increase in velocity. So this is the case of constant acceleration irrespective of increase in speed. Eg. One can experience any object falling freely in gravity.

  2. Average acceleration : The average acceleration is the total change in velocity divided by the total time. Average acceleration is calculated for long distance interval.

    So here,

    Δv = V2-V1

    Δt = T2- T1

    This can be found using the equation :

    Acceleration = (change in velocity)/(change in time)

    a = Δv ÷ Δt. 

  3. Deceleration /Negative acceleration : When the velocity of an object decreases this is called deceleration. This is represented by a negative acceleration which is observed opposite to the velocity.