Question

a pebble is dropping from a building that is 125m high. THe pebble is initially at rest. approximately how long does it take for the pebble to reach the ground.

Answer 1

Here's the formula you want to use to solve this:

Distance = (1/2) · (acceleration) · (time²)

We know the distance to the ground and the acceleration of gravity, so let's pluggum in:

. . . . . 125 m = (1/2) (9.8 m/s²) (time²)

Divide each side by (4.9 m/s²):

. . . . . (125 m) / (4.9 m/s²) = time²

. . . . . 25.51 s² = time²

Square-root each side:

5.05 seconds = time