- #1

cidilon

- 11

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## Homework Statement

Andrew is driving his van to deliver groceries in Elmvale. As he travels along Hwy 92, a fox stops on the road. Andrew is traveling at 75 km/h [North] and is 42 m away from the fox when he applies his brakes. It takes him 3.4 s to stop.

a) How far did Andrew travel before stopping?

v1 = -75 km/h [North] or -20.8 m/s [North] (It has to be negative because he is decelerating, right?)

v2 = 0

t = 3.4 s

## Homework Equations

From looking at some examples, i believe i am supposed to use

d = .5(v2-v1)t + v1*t

or if i find acceleration first

d = v1*t + .5*a*t*t

## The Attempt at a Solution

d = .5(v2-v1)t + v1*t

d = .5*(0+20.8)*3.4 - 20.8*3.4

d = -35.36 m [North] or -35 m [North]

As final velocity is known, can i use d = v2*t - .5(v2-v1)t or d = .5(v2+v1)t instead and does it matter?

What i am confused about is that d = .5(v2+v1)t is the area of a trapezoid, where as the slope as i imagine it for this word problem, makes a triangle. How is the area of a trapezoid working for a triangle? Does the slope NOT make a triangle? Should i not visualize this problem?

I really hope that i made myself clear, as it has been bugging me quite a lot!