# Homework Help: Solving distance in this problem. Easy

1. Feb 27, 2013

During the braking test of. 1988 car, the car came to rest from an initial velocity of 96km/h (w) in 3.0 seconds. Assuming that deceleration remains constant.

How far did the car travel after brakes were applied?

I calculated the deceleration. It is 8.9m/s (e)
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 27, 2013

### Staff: Mentor

Keep going...

3. Feb 27, 2013

I used this equation to solve for Distance.

Vf^2 - vi^2/ 2 aav

VHF is final velocity and vi is initial velocity, aav is average velocity

=0^2 - 96^2/ 2 (8.9)

=-517.75

...

4. Feb 27, 2013

There

5. Feb 27, 2013

### SammyS

Staff Emeritus
This equation is missing something.[/QUOTE]

One thing is an equal sign (so it's not an equation).

It's missing something else also.

6. Feb 27, 2013

### sjb-2812

Are you sure? This seems wrong to me (units?)

7. Feb 27, 2013

8.9 is the deceleration.

My question is

How far did the car travel after brakes were applied?

8. Feb 27, 2013

### CWatters

Nope. As sjb-2812 has suggested the units are wrong. It should be 8.9 m/s2

I would use a different equation of motion...

http://en.wikipedia.org/wiki/Equations_of_motion#SUVAT_equations

eg..

V2 = U2 + 2as

so

s = (V2 - U2)/2a