What is acceleration, in simple words?
Acceleration is how quickly your speed changes. If a car gains 5 metres per second of speed every second, its acceleration is 5 m/s².
// physics › Acceleration
Acceleration
Find acceleration from the change in velocity over time, or solve for final/initial velocity or time, using a = (v - u)/t.
a = (v − u) / t
Frequently asked questions
What do u, v and t mean?
u is your starting velocity, v is your final velocity, and t is the time taken. The formula is a = (v − u) ÷ t — the change in velocity divided by the time.
Can you show an example?
A car goes from rest (u = 0) to 20 m/s (v = 20) in 4 seconds. Acceleration = (20 − 0) ÷ 4 = 5 m/s². It gains 5 m/s of speed every second.
What does negative acceleration mean?
It means slowing down (deceleration). If the final velocity is less than the starting velocity, v − u is negative, so the acceleration comes out negative — the object is braking.
What are the units?
Velocity is in metres per second (m/s) and time in seconds, so acceleration is in metres per second squared (m/s²). For comparison, gravity speeds a falling object up by about 9.81 m/s².
Where do I see acceleration in real life?
A car pulling away from traffic lights, a plane speeding up for take-off, or a ball you drop falling faster and faster — all are acceleration.