# Thread: question . Functions, Domain & Range

1. ## question . Functions, Domain & Range

Please help ASAP with this question i've been going at this for 2hrs my brains is going to explode ...

1. "The stopping distance of a car on dry asphalt can be modelled by the function d(s) = 0.006s^2, where d(s) is the stopping distance, in metres, and s is the speed of the car in kilometres per hour. The stopping distance for a car on wet asphalt can be modelled by the function d(s) = 0.009s^2. The stopping distance for a car on ice can be modelled by the function d(s)=o.o4s^s"

2. "Write a reasonable domain and range for each of the functions d(s)=0.006s^2, d(s)=0.009s^2, and d(s)=0.04s^2"

2. ## Re: question . Functions, Domain & Range

The stopping distance d(s) will always be non-negative.
Since a car can go backwards and forwards, s can be negative or positive.
However, due to the limitations of car speeds, s could probably only exist in a reasonable domain.

If I had to answer, I would start out by "assuming" that a car can only have speeds from [-50, 120].
Now graph the d(s) functions. The lowest value of d(s) should be 0, and the highest values should be on the endpoints.

3. ## Re: question . Functions, Domain & Range

According to Wikipedia and the World of Physics, speed is a nonnegative value as the absolute value (magnitude) of the velocity.

4. ## Re: question . Functions, Domain & Range

So I would put the domain of s as [0,120].

5. ## Re: question . Functions, Domain & Range

Originally Posted by shuckle1729
So I would put the domain of s as [0,120].
Yes, unless you never wanted to drive faster!