Understanding the Concepts

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

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

Formula

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

* v = u + at

Where:

* v = final velocity (what we want to find)

* u = initial velocity (0 m/s since the ball is dropped)

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

* t = time (4.5 seconds)

Calculation

1. Substitute the values into the formula:

v = 0 + (9.8 m/s²) * (4.5 s)

2. Calculate:

v = 44.1 m/s

Answer:

The speed of the ball when it reaches the ground is approximately 44.1 m/s.