1. The problem statement, all variables and given/known data
A truck is traveling down the road at 60 mph, and begins to decelerate at a rate of 0.8 g.
I’d like to find the total distance it takes the truck to stop, and come up with a formula for the velocity as a function of displacement from the original braking point.
2. Relevant equations
I think that the relevant equation is v2 = 2a(s2-s1)+v12
3. The attempt at a solution
Well, I know the truck is traveling at 88 fps, and slowing at a rate of 0.8 * 32fps2, so it will take
88 fps / (32.2 fps2 * 0.8 g) * 44 fps = 150 feet to stop
But when I plug those numbers into the above equation, I get
v2 = (2 * (0.8 * 32.2 * 60 / 88) * (-x) + (60)2)0.5
That has the right y-intercept (65 mph), but the wrong x-intercept, around 104′
If I change the "2" on the right side of the equation to 1.38, it looks right, but I can’t work out why it would be 1.38 instead of two.
Argh! Any help much appreciated!