Question

If a ball that is 4 meters above the ground is thrown horizontally at 4 m/s, how long will it take the ball to hit the ground?

Answer 1

The time it will take to reach the ground is

$$t=\sqrt{\frac{2h}{g}}=\sqrt{\frac{2·4}{9.8}}=0.9\text{ s}.$$

The time does not depend on the horizontal speed.