Kinematics · 19 min
Acceleration
Speeding up, slowing down, or turning — all of it counts.
Why should I care?
A car rounds a bend at a perfectly constant speed. Is it accelerating?
Yes — because its direction is changing, its velocity is changing, and any change in velocity is acceleration, even without speeding up or slowing down.
Explore
Slope of the slope
On a velocity-time graph, acceleration is the slope. A flat line means constant velocity — zero acceleration. A straight sloped line means constant acceleration.
The idea
The rate velocity changes
Acceleration is the rate of change of velocity with time. It's a vector too — positive acceleration doesn't always mean speeding up, and negative doesn't always mean slowing down. It depends on the direction of the velocity itself.
True or false?
Negative acceleration always means an object is slowing down.
Worked example
Worked example
A skater speeds up from 2 m/s to 14 m/s in 4 s. Find the acceleration.
- 1
Find the change in velocity: 14 − 2 = 12 m/s.
Your turn
A ball thrown upward slows down as it rises. What direction is its acceleration?