Understanding the Concepts

* Acceleration due to gravity: Near the Earth's surface, objects fall with a constant acceleration due to gravity, denoted by 'g'. The standard value of 'g' is approximately 9.8 m/s².

* Uniform acceleration: Since the acceleration due to gravity is constant, the ball's motion is considered uniformly accelerated.

Using the Equations of Motion

We can use one of the standard equations of motion for uniformly accelerated objects:

* v = u + at

Where:

* v = final velocity (20 m/s)

* u = initial velocity (0 m/s, since it starts from rest)

* a = acceleration (what we want to find)

* t = time (2 seconds)

Solving for Acceleration

1. Substitute the values into the equation:

20 m/s = 0 m/s + a * 2 s

2. Simplify:

20 m/s = 2a s

3. Solve for 'a':

a = 20 m/s / 2 s

a = 10 m/s²

Answer: The ball's acceleration is 10 m/s².

Important Note: This answer is slightly different from the standard value of 'g' (9.8 m/s²). This is likely due to rounding or the specific scenario in the problem.