What is Acceleration?
Acceleration is how quickly an object's velocity changes over time — a core idea of motion and the link between velocity and force.
Acceleration is the rate of change of velocity: a = Δv/Δt, in m/s². Speeding up, slowing down and changing direction all count.
Try it: interactive calculator
Step-by-step worked examples
A car speeds up from 10 m/s to 30 m/s in 4 s. Find its acceleration.
Δv = 30 − 10 = 20 m/s a = Δv/Δt = 20/4 = 5 m/s²
A cyclist slows from 12 m/s to 0 in 6 s.
Δv = 0 − 12 = −12 m/s a = −12/6 = −2 m/s²
From rest at 3 m/s² for 5 s, final velocity?
Δv = a·Δt = 3×5 = 15 m/s
Flashcards
Quick quiz
Q1.0→20 m/s in 5 s. Acceleration?
Q2.Unit of acceleration?
Q3.Negative acceleration means…
Q4.Circular motion at constant speed…
The full card deck, worked steps and AI-tutor support for “What is Acceleration?” are in Notek — study by hand before your exam.
Common mistakes
Confusing velocity and acceleration. — Correct: Velocity = how fast; acceleration = how fast velocity changes.
Zero velocity = zero acceleration. — Correct: A dropped ball at rest still accelerates.
Ignoring sign. — Correct: Negative = slowing down.
Direction changes don't count. — Correct: They do — velocity is a vector.
FAQ
What is the formula for acceleration?
a = Δv/Δt — change in velocity over time. Unit: m/s².
Difference between speed and acceleration?
Speed is how fast; acceleration is how fast velocity changes.
Can acceleration be negative?
Yes — deceleration is negative acceleration.
Is acceleration a vector?
Yes, in the direction of the net force.