You figure out how long it would take a car traveling at 25 mph
to cover 360 ft. Any driver who does it in less time is speeding.

   (25 mi/hr) · (5,280 ft/mile) · (1 hr / 3,600 sec)

   = (25 · 5280 / 3600) ft/sec = (36 and 2/3) feet per second.

To cover 360 ft at 25 mph, it would take

360 ft / (36 and 2/3 ft/sec) = 9.82 seconds .

Anybody who covers the 360 feet in less than 9.82 seconds
is moving faster than 25 mph.
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If you're interested, here's how to do it in the other direction:

Let's say a car covers the 360 feet in ' S ' seconds.
What's the speed of the car ?

   (360 ft / S sec) · (1 mile / 5280 feet) · (3600 sec/hour)

   = (360 · 3600) / (S · 5280) mile/hour

   = 245.5 / S miles per hour .

The teacher timed one car crossing both strips in 7.0 seconds.
How fast was that car traveling ?

   245.5 / 7.0 = 35.1 miles per hour

Another teacher timed another car that took 9.82 seconds to cross
both strips. How fast was this car traveling ?

245.5 / 9.82 = 25 miles per hour

7 0

2 years ago