Two automobiles drive in the same direction along
a snow-covered road. Each moves initially at speed
20 m/s (about 40 mph),
and the distance between them is D meters.
A deer jumps into the road just 30m (about 100 feet)
in front of car B.
The driver takes TB
to react to the even, after which he slams on the brakes.
This car, with good snow tires,
decelerates at 2 m/s2.
The driver of the following car, A, doesn't notice
the deer, but does see the brake lights of the car in front
of him light up. He takes TA
to react -- a longer time because this isn't
such a dramatic event.
When he hits his brake pedal, the older tires
decelerate car A at 1.5 m/s2.
- How far does car B travel before coming to a stop?
What is the fate of the deer?
- How far does car A travel before coming to a stop?
- How large a distance must there be between cars
to prevent a collision?
- How many "car-lengths" should there be between cars
for safety?
- How many "seconds-of-time" should there be between cars
for safety?
