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## Homework Statement

The driver of a pickup truck going 100 km/h applies the brakes, giving the truck a uniform deceleration of 6.50 m/s^2 while it travels 20.0 m.

a) what is the speed of the truck in kilometers per hour at the end of this distance?

b) How much time has elapsed?

## Homework Equations

## The Attempt at a Solution

The first thing I did was convert 100 km/h into m/s and got 277.7 m/s.

After converting I tried using V^2= V(initial)^2 x 2(a)x, where a = acceleration and x = horizontal distance.

I got

V^2 = (277.7 m/s)^2 + 2 (-6.50 m/s^2) (20.0-0)

V^2 = 77117.29 + (-260)

V^2 = 76857.29

V= 277.23 m/s which equates to 99.8 km/hr which makes no sense.

I then tried x = x(initial) + 1/2 at^2 to try and acquire time first.

I ended up getting 83 seconds. Which is way off. So I checked the answers in the back of the book and it read:

for part a) 81.4 km/h

b) .794 s

can someone please tell me what I'm doing wrong? I'm obviously not asking for the answer since I've got the book.