A glass falls off a shelf. How fast is the glass moving after 0.4 seconds?

On Earth, gravity increases the speed of a falling object by about 9.8 m/s

every second that it falls.

In 0.4 second, its speed increases by (0.4 x 9.8) = 3.92 m/s.

If it just rolled off of the shelf at the beginning of that 0.4 second, then it

started from zero speed, and its speed after 0.4 second is 3.92 m/s.

Its velocity is 3.92 m/s downward.