Finding the time it takes to stop

[missashley]

Homework Statement

A 2410 kg car traveling to the west at 22.6 m/s slows down uniformly.

How long would it take the car to come to a stop if the force on the car is 8880 N to the east? Answer in units of s

What is the car's displacement during the time it takes to stop? Answer in m

Homework Equations

d = .5at^2 + Vit

The Attempt at a Solution

2410 * 22.6 = 54466 kg*m/s (the momentum)

8880 N is also 8880 kg*m/s^2

54466 / 8880 = 6.133558559 seconds (this is right)

d = .5at^2 + Vit
d = (.5)(22.6/6.13355)(6.13355^2) + (22.6*6.13355)
d = 207.9273 m

I got the time, but when i plug in the displacement it's wrong

 

[marcusl]

The acceleration is directed opposite to the initial speed, so you must be careful about signs.

 

[missashley]

The acceleration is directed opposite to the initial speed, so you must be careful about signs.

hmmmm