Question

The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car travelling 80 mph can stop in 400 ​ft, how many feet will it take the same car to stop when it is travelling 64 ​mph?

Answer 1

The distance to stop is 256 ft

Step-by-step explanation:

The displacement of car is given as directly proportional to its speed

Thus ( 80 )² ∝ 400 I

Similarly in second case

( 64 )² ∝ S II

dividing II by I

`(80^2)/(64^2)` =
`(400)/(S)`

here we are to find the S displacement

Thus S = 256 ft