Understanding the Concepts

* Free Fall: The rock is in free fall, meaning the only force acting on it is gravity.

* Acceleration due to Gravity: The acceleration due to gravity (g) is approximately 9.8 m/s². This means the rock's velocity increases by 9.8 meters per second every second it falls.

Using the Equations of Motion

We can use the following equation to find the final velocity (v):

* v = u + at

Where:

* v = final velocity

* u = initial velocity (0 m/s since the rock starts from rest)

* a = acceleration due to gravity (9.8 m/s²)

* t = time (1.5 s)

Calculation

1. Plug in the values:

v = 0 + (9.8 m/s²) * (1.5 s)

2. Calculate:

v = 14.7 m/s

Answer: The velocity of the rock when it hits the ground is 14.7 m/s.