Acceleration
Acceleration is the rate of change of velocity.
About this topic
Acceleration is the rate at which velocity changes: a = (v - u)/t, measured in m/s². It occurs when speed increases, decreases (negative acceleration or deceleration) or direction changes. A car going round a bend at steady speed is accelerating, because its velocity vector is turning.
Constant acceleration of 3 m/s² means velocity rises by 3 m/s every second: from rest, you would be at 3 m/s after 1 s, 6 m/s after 2 s and 9 m/s after 3 s. Acceleration is a vector, so its sign matters. Speeding up in the positive direction gives positive acceleration, but slowing down while moving positive gives negative acceleration.
Example: a sports car goes from 0 to 27 m/s (about 100 km/h) in 4.5 s, so a = 27/4.5 = 6 m/s². Passengers feel acceleration as a push in their seats, and engineers design brakes, lifts and roller coasters around acceptable acceleration limits.
Misconceptions: zero velocity does not mean zero acceleration, since a ball at the top of its throw has zero velocity but still accelerates downward at 9.8 m/s². Also, a negative acceleration does not always mean slowing down; it depends on the direction of the velocity as well.
Key ideas
- a = Δv / Δt
- Speeding up, slowing down and turning all accelerate
- Units are m/s²
Quick check
Use cases: where Acceleration helps
- Homework: review the key idea behind Acceleration before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Acceleration without notes.
- Visual learning: play with the interactive lab to see how Acceleration changes when you adjust its inputs.
- Teaching a friend: explain Acceleration in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Acceleration?
Acceleration is the rate of change of velocity.
What will I learn in Acceleration?
a = Δv / Δt. Speeding up, slowing down and turning all accelerate. Units are m/s².
Is Acceleration part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Acceleration lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Acceleration?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.