# Homework Help: What am I missing here?

1. Sep 25, 2007

### UpperNinety08

[SOLVED] What am I missing here?

1. The problem statement, all variables and given/known data

A sports car is advertised to be able to stop in a distance of 50 m from a speed of 90 km/h. What is its acceleration in m/s²?

2. Relevant equations

v² = v0² + 2a(x-x0)

3. The attempt at a solution

I attempted to solve for a using this equation, but came out with a value like 6 m/s² which I don't believe is correct. The first thing I did was multiply 90 km/h by .2777777 to convert it to m/s which gave me roughly 25 m/s. I plugged in 625 in for v0² (25²) and divided that by 50 m (50 - 0). I got 12.5 which after divided by 2 gave me 6.25, which like I said above I can't imagine is correct. Help :(

2. Sep 25, 2007

### Kurdt

Staff Emeritus
You seem to have done everything perfectly, except perhaps the sign of the acceleration. Why do you not think think its correct?

3. Sep 25, 2007

### UpperNinety08

I don't know I'm just really bad at this stuff. Thanks for the clarification anyway.

4. Sep 25, 2007

### Kurdt

Staff Emeritus
A very simple way to check is to just put the value back into the equation and see if it does what you expect. In this case you would expect the final velocity to be 0. Or in other words, both terms on the right hand side would have to be equal.