Acceleration
How quickly velocity changes. Acceleration = change in velocity / time, measured in m/s squared.
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Analogy
Pressing the accelerator and watching the speedometer climb every second.
Example
start 0 m/s, end 20 m/stime = 8 sa = (20 - 0) / 8a = 2.5 m/s squared
In practice
A negative acceleration (deceleration) is a car slowing down when the brakes go on.
Practice
Flashcards
- What is the formula for acceleration?Acceleration = change in velocity / time, in m/s squared.
Interview questions
- A train speeds up steadily from 5 m/s to 25 m/s in 10 s. Calculate its acceleration and the distance it covers in that time.
- Acceleration = (25 - 5) / 10 = 2 m/s squared
- Average velocity = (5 + 25) / 2 = 15 m/s
- Distance = 15 x 10 = 150 m
- Give units with each answer
Questions people ask
What does an acceleration of 2 m/s squared mean?
It means the velocity goes up by 2 m/s every second. If you start at rest, you are moving at 2 m/s after one second, 4 m/s after two seconds, and 6 m/s after three. The unit m/s squared is just 'metres per second, per second'.
Is slowing down also acceleration?
Yes. Physicists use acceleration for any change in velocity, including slowing down. Slowing down gives a negative acceleration, sometimes called deceleration. A car braking from 30 m/s to 10 m/s in 4 s has an acceleration of -5 m/s squared.