A rock is dropped from a vertical cliff. The rock takes 3.00 s to reach the ground below the cliff. A second rock is thrown vertically from the cliff. It takes 2.00 s to reach the ground below the cliff from the time it is released. With what velocity was the second rock released?
A)4.76 m/s upward
B)5.51 m/s downward
C)12.3 m/s upward
D)4.76 m/s downward
E)12.3 m/s downward

Question

Quizplus · Accepted Answer

The time taken by the second rock is less than the first, indicating it was thrown downward. Using the equation of motion $ s = ut + \frac{1}{2}gt^2 $, and knowing the first rock's time gives the height, solve for the initial velocity of the second rock.

A Rock Is Dropped from a Vertical Cliff