i have to agree with the other tutor, theres many other facters such as type of vehicle via a sports car or a semi. also 4 wheel drive or disc brakes. wheather conditions road conditions, flat or hill like roads, obsticales, wind resistance, reaction time of driver average, old or a newb driver, wear and tear on the vehicle like break pads and pressure of break pedal. distractions on or near road or in the car..like texting and driving.
once your able to answer all this other stuff then maybe there might be a real answer. but the best answer is: it varies with different drivers.
there is a 3 sec road rule in following other cars, so the average driver will have enough time to slam on the brakes and stop in time. but with factors like ice and down hill brakes dont even matter. just look it up on youtube quite funny.