Question

The function d(s) = 0.0056s squared + 0.14s models the stopping distance

of a car, d(s), in metres, and the speed, s, in kilometres per hour. What
is the speed when the stopping distance is 7 m? Use a graph to solve.​

Answer 1

The car must have a speed of 25 kilometres per hour to stop after moving 7 metres.

Explanation:

Let be
`d(s) = 0.0056\cdot s^(2) + 0.14\cdot s`, where
`d` is the stopping distance measured in metres and
`s` is the speed measured in kilometres per hour. The second-order polynomial is drawn with the help of a graphing tool and whose outcome is presented below as attachment.

The procedure to find the speed related to the given stopping distance is described below:

1) Construct the graph of
`d(s)`.

2) Add the function
`d = 7\,m`.

3) The point of intersection between both curves contains the speed related to given stopping distance.

In consequence, the car must have a speed of 25 kilometres per hour to stop after moving 7 metres.