The acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8 m/s2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?

Given Information:  

Acceleration of gravity = g = 9.8 m/s²

Time period = t = 3 seconds

Required Information:

velocity = v = ?

v = 29.4 m/s

Explanation:  

As we know the velocity of an object under free fall assuming that the object was initially at rest is given by

v = -gt

Where minus sign indicates that the object is moving downward

v = -9.8*3

v = -29.4 m/s

Therefore, the rock will be falling at the speed of 29.4 m/s after 3 seconds.

probably not if net force is zero