A car is traveling with a constant speed when the driver suddenly applies the brakes, causing the car to slow down with a constant acceleration of magnitude 3. 50 m/s2. If the car comes to a stop in a distance of 30. 0 m, what was the car's original speed?.

14.49 m/s

Explanation:  you would have to use  kinematic equations to solve for the original speed.

v^2 = v0^2 + 2 (a) (x)  where v = 0 since the car stopped

then you would get v0 = sqrt (2(a)(x))

plug in the known values

v0 = sqrt(2(3.50)(30.0))

v0 = 14.49 m/s

So the answer would be 14.49 m/s

foucusing is the hope this works for you (: