Question

f a car is speeding down a road at 40 miles/hour (mph), how long is the stopping distance D40 compared to the stopping distance D25 if the driver were going at the posted speed limit of 25 mph? Express your answer as a multiple of the stopping distance at 25 mph. Note that D25 is already written for you, so just enter the number. View Available Hint(s)

Answer 1

D40 = 2.56 × D25

so number is 2.56 multiple of stopping distance @ 25 mph

Step-by-step explanation:

given data

speed = 40 miles / hour

distance = D40

speed limit = 25 miles / hour

distance = D25

to find out

express number a multiple of stopping distance @ 25 mph

solution

we know here stopping distance is directly proportional to (speed)²

so here speed ratio is

initial speed =
`(40)/(25)`

so initial speed = 1.6

so

stopping distance increase = (1.6)²

`(D40)/(D25)` = (1.6)²

`(D40)/(D25)` = 2.56

so here

D40 = 2.56 × D25

so number is 2.56 multiple of stopping distance @ 25 mph