This depends on your speed. From a legalistic standpoint, there is no set distance; that's not to say you wouldn't get pulled over for tailgating. In general, you should keep enough distance between you and the vehicle in front of you so that if they were to suddenly slam on the brakes, you wouldn't hit them.
550 feet.
Everybody gets lost while driving once in a while.
A minimum of 2 seconds in good weather.
100 feet.
Yes there are laws regarding texting while driving in many states.
2
It is traveling at about 58.66 feet per second.
Many accidents are the result of reckless driving or driving while intoxicated.
Square feet are used to measure area, while feet are used to measure distance. They are not equivalent, and so cannot be converted from one to another.
400 ft
72 Feet
100 yards