Question

A pebble falls off the top of a cliff. Its final velocity is 58.8m/s. How long does it take to reach the ground? Show
your work.

Answer 1

Answer: 5.7s

Step-by-step explanation:

We are explicitly given the final velocity of 58.8m/s, and implicitly given the acceleration of 9.8m/s^2 due to gravity. We are also implicitly given the initial velocity of the pebble. The pebble was not thrown off the cliff, it simply fell off the cliff. Therefore the initial velocity is 0m/s. Using the first kinematic equation, you get:

$v_f=v_i+at$

$58.8=0+(9.8)t$

$58.8=9.8t$

$t=5.7s$