A ball is thrown straight up at 16.8 m/s. How high does it rise? Leave out the air. (g = 9.8 m/s²)

Step 1. $\tfrac{1}{2}mu^2 = mgh$, so $h = \dfrac{u^2}{2g}$.

Step 2. $h = \dfrac{(16.8\ \text{m/s})^2}{2 \times 9.8\ \text{m/s}^2} = \dfrac{282.24\ \text{m}^2/\text{s}^2}{19.6\ \text{m/s}^2} = 14.4\ \text{m}$.