Question

what keeps changing in case of an object in uniform circular motion​

Answer 1

Accelerating objects are objects which are changing their velocity - either the speed (i.e., magnitude of the velocity vector) or the direction. An object undergoing uniform circular motion is moving with a constant speed. Nonetheless, it is accelerating due to its change in direction.

Answer 2

Answer:

An object undergoing uniform circular motion is moving with a constant speed. Nonetheless, it is accelerating due to its change in direction. ... Yet, with the inward net force directed perpendicular to the velocity vector, the object is always changing its direction and undergoing an inward acceleration.