A ball is dropped from a bridge 20 m tall. Calculate the time it will take the ball to reach the ground (free fall time)

1. Identify the initial conditions:

- Initial height, h = 20 \, \text{m}
- Initial velocity, v_0 = 0 \, \text{m/s} (since the ball is dropped)
- Gravitational acceleration, g = 9.8 \, \text{m/s}^2

2. Use the formula for the distance under constant acceleration to solve for time ( t ):

h = v_0 t + \frac{1}{2} g t^2

3. Plug in the known values:

20 = 0 + \frac{1}{2} \cdot 9.8 \cdot t^2

4. Simplify the equation:

20 = 4.9 t^2

5. Solve for t :

t^2 = \frac{20}{4.9}

6. Calculate the square root:

t = \sqrt{\frac{20}{4.9}}

7. Thus,

t \approx 2 \, \text{s}