If you drop a rock from 700 meters high, how long will it take the hit the ground? (Remember to make height negative when solving because it is falling)
5
10
11.95
7.95

The correct option is;

11.95

Explanation:

The given parameters are;

The height from which the rock is dropped = 700 meters

The time for the to hit the ground is given by the relation, h = u·t + 1/2·g·t²

Where;

h - The height = 700 meters

u = The initial velocity = 0

t = The time taken for the rock to cover the height, h, and hit the ground

g = The acceleration due to gravity = 9.81 m/s²

Therefore, we have by substitution,

700 = 0 × t + 1/2 × 9.81 × t²

∴ t = √(700/(1/2 × 9.81)) ≈ 11.95

The time for the rock to hit the ground, t ≈ 11.95 seconds.

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