Concept:In uniform circular motion, speed is constant but velocity direction changes continuously, so acceleration is always present (centripetal) with constant magnitude but changing direction.
Explanation:A car in uniform circular motion moves at constant speed along a circular path.
Velocity is a vector; it changes direction every instant even if speed is constant.
This change in velocity causes an acceleration called centripetal acceleration.
Its magnitude is
a=rv2​, which remains constant because
v and
r are constant.
However, the direction of this acceleration always points toward the centre of the circle.
As the car moves, the direction of the centre changes relative to the car, so the acceleration vector rotates continuously.
Thus, the acceleration is non‑zero but its direction is not constant — only the magnitude is constant.
Therefore, the acceleration is a non‑zero vector that is not constant (i.e., it changes direction).
Answer:Option C: a non-zero but not a constant.
