In a cam drive with uniform velocity follower, the slope of the displacement must be as shown in Fig. I. But in actual practice it is as shown in Fig. II (i.e. rounded at the corners). This is because of 
(a) The difficulty in manufacturing cam profile
(b) Loose contact of follower with cam surface
(c) The acceleration in the beginning and retardation at the end of stroke would require to be infinitely high
(d) Uniform velocity motion is a partial parabolic motion