Constant speed is not zero acceleration

01
The tempting model
Assuming constant speed in a circle means no acceleration.
02
Why it feels right
“Acceleration” colloquially means speeding up, and the speed isn't changing.
03
Where it breaks · how to catch it
You set a = 0 for something moving in a curved path at steady speed.
04
The correct model
Velocity is a vector. In uniform circular motion its direction changes, so there is centripetal acceleration a = v²/r directed toward the center.
05
Repair · see it, then test it
worked example A ball on a string circles at a steady 3 m/s. Is it accelerating?
Tempting move
No — the speed is constant.
Correct move
Yes — the velocity's direction turns, giving inward acceleration v²/r.
Test the repair NL-02 · transfer

A cyclist follows a circular track at constant speed. Which statement is true?
Acceleration is zero Acceleration is tangent to the track Acceleration points toward the circle's center Acceleration points outward

Make a fresh prediction before referring to the worked example.
Then practise it on the ladder
R7Circular motion: force directionadds: Uniform circular motion has inward acceleration even at constant speed.