To determine the velocity of the ball as it strikes the ground, we can use the equations of motion. In this case, we can use the equation for free fall:
v^2 = u^2 + 2as,
where: v is the final velocity, u is the initial velocity, a is the acceleration due to gravity, and s is the distance fallen.
Since the ball falls from rest, the initial velocity u is 0. The acceleration due to gravity near the surface of the Earth is approximately 9.8 m/s^2 (assuming no air resistance).
Plugging in the values:
v^2 = 0^2 + 2 * 9.8 * 20, v^2 = 0 + 2 * 9.8 * 20, v^2 = 392, v = √392.
Calculating the square root:
v ≈ 19.8 m/s.
Therefore, the velocity of the ball as it strikes the ground is approximately 19.8 m/s.