How braking distance grows with speed

How much farther does a car need to stop at $120\ \text{km/h}$ than at $60\ \text{km/h}$? You will make the program find the braking distance at six speeds on a dry road, draw it beside a wet road, and compare.

The idea. From $v^2 = u^2 + 2as$ with the final velocity $0\ \text{m/s}$ and a deceleration $b$,

with the speed in m/s: divide km/h by $3.6$.

Your tasks.

1. Change every speed from km/h to m/s.
2. Work out the braking distance on the dry road at each speed.
3. Find how many times longer the distance is at $120\ \text{km/h}$ than at $60\ \text{km/h}$.