That depends on road conditions, tire conditions, and other factors.
A good rule of thumb, however, it to follow no closer than 2 seconds behind the vehicle in front of you.
About 73.3 feet per second at 50 mph.
Most cars can stop from 60 mph in about 100 feet or so. If the relationship is linear then a car should stop from 30 mph in about 50 feet.
Stopping Distance = about 56.25 feet.
Stopping distances are measured in feet not in seconds. At 40 mph you're traveling 58.7 feet per second. The average driver reaction time is about 3/4 second which equates to 44 feet. After applying the brakes it will take approximately 82 feet to stop the vehicle. The total stopping distance for a car traveling 40 mph will be 126 feet when you include reaction time and actual stopping distance of the vehicle. If you divide 126' x 58.7' which is the distance traveled per second you get 2.14 seconds. This is assuming you're paying attention and have average reaction time while driving.
30 feet
175 feet. The Oregon Drivers Handbook calculates it at closer to 240 feet. (of course many factors can make it more or less distance.)
50 Mph X 3.5 = 175 feet = 53.3 metressee http://www.hintsandthings.co.uk/garage/stopmph.htm for explanation and various equations
The typical BREAKING distance from 50mph is 38meters, but the overall stopping distance is 53meters (overall stopping distance is made up of thinking distance, which is 15meters in this case, + breaking distance)
Need car's weight and stopping power to compute.
About 73.3 feet per second at 50 mph.
55 feet
110 feet
Stopping Distance = about 75 feet.
Stopping Distance = 15 feet
228ft
Most cars can stop from 60 mph in about 100 feet or so. If the relationship is linear then a car should stop from 30 mph in about 50 feet.
Stopping Distance = about 146.25 feet.