A roller-coaster car starts from rest 34 m above the ground…

Step 1. (a) $\Delta h = 34\ \text{m} - 14\ \text{m} = 20\ \text{m}$: $v = \sqrt{2 \times 9.8\ \text{m/s}^2 \times 20\ \text{m}} = 19.80\ \text{m/s}$.

Step 2. (b) $\Delta h = 34\ \text{m} - 4\ \text{m} = 30\ \text{m}$: $v = \sqrt{2 \times 9.8\ \text{m/s}^2 \times 30\ \text{m}} = 24.25\ \text{m/s}$.