Understanding the Physics

* Free Fall: An object in free fall experiences only the force of gravity.

* Acceleration due to Gravity (g): On Earth, this is approximately 9.8 m/s². This means the object's velocity increases by 9.8 m/s every second.

* Initial Velocity (v₀): Since the rock is dropped, its initial velocity is 0 m/s.

Formula

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

v = v₀ + at

where:

* v = final velocity

* v₀ = initial velocity

* a = acceleration due to gravity (g)

* t = time

Calculations

1. Plug in the values:

* v₀ = 0 m/s

* a = 9.8 m/s²

* t = 2.5 s

2. Substitute into the equation:

v = 0 + (9.8 m/s²)(2.5 s)

3. Calculate:

v = 24.5 m/s

Answer: The rock's velocity as it reaches the ground is 24.5 m/s.