# Acceleration

Last updated on February 8th, 2024 at 12:30 pm

**Any variation from moving at a constant speed in a straight line is described as 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: