One important factor in driving a car is stopping safely. The time to stop a car safely depends on the speed the car is moving when we want to stop. It takes the average driver about 0.75 of a second to react before actually stepping on the brake pedal. Once the brake has been depressed, it takes additional time before the car comes to a complete and safe stop.

The table below shows the minimum stopping distances for various car speeds. It shows the number of feet to traveled due to reaction time and the distance in feet to safely stop  the car. Finally, a total stopping distance is shown.

There are three equations to calculate these distances.

RT (reaction-time distance (ft.))= 1.1 ´ speed (mph)

BD (braking distance (ft.))=0.06 ´ speed (mph) 2

TSD (total stopping distance (ft.))=1.1 ´ speed (mph) + 0.06 ´ speed (mph) 2

This table provides the minimum stopping distance on a dry, level, and concrete surface.

 Speed (mph) Reaction Distance (ft) Brake Distance (ft) Total Stopping Distance (ft) 10 11 6 17 20 22 24 46 30 33 54 87 40 44 96 140

Calculate the stopping distances for 50 mph using the above equations.

For 50 mph

RT = 1.1 ´ 50

= 55 feet reaction-time distance

BD = 0.06 (50 ´ 50)

= 150 feet braking distance

TSD = 1.1 ´ 50 + 0.06 ´ (50 ´ 50)

= 205 feet shopping distance

Calculate the stopping distances for 60 mph.