Question

In which motion, momentum changes but K.E. does not?

Answer 1

In uniform circular motion linear momentum changes but kinetic energy does not.

This is because in circular motion, linear velocity keeps on changing at each and every point

as it is a vector quantity.

Momentum or linear momentum is velocity dependent and thus it changes as velocity changes

because it is a vector quantity as well.

But since kinetic energy is not a vector quantity it doesn't change in circular motion.