Question

We want to design an airport runway with the following specifications. The lowest acceleration of a plane should be  

4m/s2

and its take-off speed is 75 m/s. How long would the runway be to allow the planes to accelerate through it?

Answer 1

$$v=v_0+at$$

$$t=\frac{v-v_0}{a}=\frac{75-0}{4}=19\:\rm s$$