Aball rolls horizontally off a table of height 0.6 m with a speed of 9 m/s .how long does it take the ball to reach the ground?

The distance an object falls from rest is

                     D  =  (1/2) (gravity) (time)² .

If the ball falls 0.9 meter, then

                               0.9 m  =  (1/2) (9.8 m/s²) (time)²

Divide each side
by 4.9 m/s² :           0.9 m / 4.9 m/s² = time²

Take the square root
of each side:                time = √(0.9/4.9) sec²

                                              =        0.43 second .

The horizontal motion of the ball makes no difference.
It doesn't matter whether the ball rolls off of a table,
gets dropped from a hand, or shot horizontally from
a gun. It still hits the floor or the ground 0.43 sec later.