A ball is thrown horizontally off a cliff at the same time that an identical ball is dropped off a cliff. How long after the dropped ball hits the ground will the thrown ball hit?

The correct answer is that both balls will hit the ground at the same time. When an object is dropped from a height, it begins to accelerate downward due to gravity, while a horizontally thrown object also experiences the same gravitational acceleration.

Even though the thrown ball moves horizontally, it still falls under the influence of gravity at the same rate as the dropped ball. The horizontal motion does not affect the time it takes for either ball to reach the ground, as gravity acts equally on both. They both start falling from the same height simultaneously, thus they will hit the ground at the same moment.

This principle stems from the independence of vertical and horizontal motion in physics. Therefore, regardless of the initial horizontal velocity, the time it takes for both balls to fall to the ground depends solely on the vertical height they fall from and the acceleration due to gravity.