# Acceleration

Last updated on May 16th, 2022 at 08:09 pm

## What is Acceleration?

Any variation from moving at a constant speed in a straight line is described as an acceleration.
It is very important to realize that going faster, going slower, and/or changing direction are all different kinds of acceleration (changing velocities).

Acceleration, a, is defined as the rate of change of velocity with time.
If the acceleration is constant over time Δt then it can be expressed as: a =Δv/Δt = (v − u)/t

The SI unit of acceleration is meters per second squared, m/s^2 (the same as the units of velocity/time, m/s/s).

Acceleration is a vector quantity.
Acceleration can be:
■ an increase in velocity (positive acceleration)
■ a decrease in velocity (negative acceleration – sometimes called a deceleration)
■ a change of direction.

Now if you like to know in detail about average and instantaneous acceleration, then read the following posts:
Average Acceleration
Instantaneous Acceleration

## Velocity-time graph (v-t graph) for an object falling under the effect of gravity, with and without air resistance

Here is a combined diagram showing both the graphs (i.e. v-t graphs with and without air drag)

We have 2 detailed posts that discuss how to draw V-t or velocity-time graphs with and without air-resistance(air-drag). The links are given below:

Motion graphs of vertical fall against air drag

Motion graphs of vertical fall without air resistance (i.e. free-fall)