This calculator has two purposes. It can be used for solving quadratic equations in general OR it can be used to find the speed from which a driver can just manage to react and stop in a specified distance.
EITHER complete the three boxes at the bottom of the form and click the Calculate speed button, OR rearrange your equation into the form Ax^2 + Bx + C = 0, type in your values for A, B and C into the boxes directly below and click the Calculate roots button.
A:
B:
C:
Roots =
To calculate the speed (x m/s), from which a driver can react and stop in a given distance (D metres), under a deceleration (a m/s/s), fill in the boxes below and click the Calculate speed button.
The calculator will automatically populate the boxes above with:
A = 1/(2a)
B = Reaction time
C = -D
It will choose the positive solution to the quadratic equation and provide the speed in m/s (and MPH) below.
You can use the slider to vary reaction time.