Velocity/acceleration/time to stop

[lauriecherie]

Homework Statement

The brakes on your car are capable of slowing down your car at a rate of 4.9 m/s^2.
If you are going 132 km/h and suddenly see a state trooper, what is the minimum time in which you can get your car under the 90 km/h speed limit?

Homework Equations

v(t)= at + initial velocity

(final velocity^2) - (initial velocity^2) = 2*a*delta X (change in position)

The Attempt at a Solution

I came out with 8.57 seconds. Is there some converting I maybe missed?

 

[Delphi51]

Hi Laurie, welcome to PF!
I don't know how you got 8.57. I got between 2 and 3s. Show your calc and we'll find your error.
Did you remember to convert the speeds to m/s ?

 

[lauriecherie]

Hi Laurie, welcome to PF!
I don't know how you got 8.57. I got between 2 and 3s. Show your calc and we'll find your error.
Did you remember to convert the speeds to m/s ?

No, I didn't convert. Whoops. So let me work this out again. Thanks for the advice.

 

[lauriecherie]

2.380952388 seconds. :!) Thanks soooo much for your help!

 

[Delphi51]

Most welcome!