The stopping distance $d$ of an automobile is directly proportional to the square of its speed $v$. A car required $40$ feet to stop when its speed was $60$ miles per hour. Find a mathematical model that gives the stopping distance $d$ in terms of its speed $v$.
Your answer is $d=$ Estimate the stopping distance if the brakes are applied when the car is traveling at $53$ miles per hour.
Your answer is: