If force is always perpendicular to motion :
(i) kinetic energy remains constant
(ii) work done is zero
(iii) velocity is constant
(iv) speed is constant

When the force is always perpendicular to motion, the speed remains constant but the direction of the motion and hence the velocity changes continuously. Also work done is always zero (because force is perpendicular to motion) and therefore the kinetic energy remains constant (from work-energy theorem).