stopping distance

Question

The stopping distance on wet pavement at 20 mph is about 60 feet. The stopping distance at 30mph it is about 120 feet. What would you estimate the stopping distance is at 40mph? Construct a formula for this.

Answer 1

(20, 60) and (30, 120) are two points on a linear graph with slope = 60/10 = 6

y=mx + b with m=6

y=6x +b plug in either point to solve for b

60= 6(20) + b

b =-60

y=6x -60

f(x) = 6x -60

f(40)= 6(40) -60 = 240-60 = 180 feet stopping distance at 40 mph