• The height $H$ of a projectile above the ground after $t$ seconds is given by the formula ${H}_{t} = - \frac{1}{2} \cdot g \cdot {t}^{2} + {V}_{0} \cdot t + {H}_{0}$,
where $g$ is a physical constant (gravitational acceleration $\approx 9.8 \frac{m}{s} ^ 2$), ${V}_{o}$ is the initial velocity and ${H}_{0}$ is the initial height.
We notice that this is a quadratic equation of variable $t$.