Actually, the majority that can drive now is level of high school above, move quickly to divide evenly not should unfamiliar, best now car, check on quite good road surface, by drive a hand professionally to hold accuse, arrive from slam the brakes on of 100km/h of speed per hour jockey, brake distance has those who be less than 40 meters rarely, a what concept is this? It is decelerate of average stop a car spend the left and right sides that it is 1g. And to divide evenly retarded motion brake is apart from S=V*V/2a, the distance difference that the brake distance of real test follows cipher out of formula of the retarded motion that use divide evenly is not big.

And the car that we drive, brake decreases speed to want far under 1g, arrive in 0.6g commonly between 0.9g, take China car to be exemple, its 100km/h is 45 meters to the test result of 0, with this cipher out its urgent Buddhist templeput on the brakes decreases speed on average to be 0.86g. We assume from see block up be 0.5 second to the time that steps on next brake pedal to make stop a machine by cutting off the power effective, be apart from at the brake of 0.86g accordingly is:

40km/h:12.76 meters;

60km/h:25.54 meters;

80km/h: 39.92 meters;

100km/h:58.9 meters;

120km/h:81.49 meters

Najieshida calculates, the biggest slowdown spends this car to have 0.7g only, assume reaction time is 0.5 second, urgent Buddhist templeput on the brakes steps dead! Criterion the data of each speed is above:

40km/h:14.37 meters;

60km/h:28.17 meters;

80km/h:46.38 meters;

100km/h:69 meters;

120km/h:96.03 meters.

If you did not step on dead brake, reduce rate even small, say to have 0.5g only for example, corresponding brake distance is:

40km/h: 17.9 meters

60km/h: 36.11 meters

80km/h: 60.49 meters

100km/h: 91.05 meters

120km/h:127.77 meters

Pass by mouth should be put 40 arrive under sexagesimal speed per hour, prep above the odds of 60 problems is very big.