What is acceleration?
In everyday life, most of the objects we see are moving with velocities that are not uniform.
Vehicles on the road are constantly having to speed up or slow down, or else to change the direction they are travelling in. The result in every one of those cases is the same: the velocity changes.
Acceleration
The rate of change of velocity is called acceleration. That is, the change of velocity in unit time.
acceleration = change in velocity ÷ time
Working through an example
| Time t (s) | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|---|
| Velocity v (m s−1) | 0 | 2 | 4 | 6 | 8 | 10 | 12 |
The calculation
change in velocity = final velocity − initial velocity = 12 − 0 = 12 m s−1
time taken = 6 s
acceleration = 12 m s−1 ÷ 6 s = 2 m s−2
Why the unit is m s−2
We already know velocity is measured in m s−1. Acceleration is the change of velocity per second, so its unit is m s−1 ÷ s, which is m s−2.
How to read 2 m s⁻²
It means "the velocity of that object increases by 2 m s−1 every second". That is exactly why the values in the table go 0, 2, 4, 6 and so on.