A ball 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.