Arock falls off a cliff and hits the ground after three seconds. what is its velocity right before it hits the ground?

9.8 m/s

0.31 m/s

29.4 m/s

3.3 m/s

The correct answer is 29.4 m/s.

The right formula to use for the scenario given in the question is:

Vf = Vi + at

Where: Vf = Final velocity = ?

Vi = Initial velocity = 0

a = Acceleration [due to gravity] = 9.8 m/s

T = Time = 3 s

Note that an object that is falling down from a height has an initial velocity of zero.

Vf = 0 + [9.8 * 3] = 29.4

Therefore, final velocity = 29.4 m/s.