A girl throws a rock horizontally, with a velocity of 10 m/s, from a bridge. It falls 20 m to the water below. How far does the rock travel horizontally before striking the water?

20 m

Explanation:

The initial vertical velocity is 0. We can find the time (t) that it takes to fall 20 m (h) using the following expression.

h = 1/2 * g * t²

where,

g is the acceleration due to the gravity

t = √ (2h/g) = √ (2 * 20 m / 9.8 m/s²) = 2.0 s

The rock is in the air during 2.0 s and moves horizontally at a constant speed of 10 m/s. The horizontal distance traveled is:

d = v * t = 10 m/s * 2.0 s = 20 m