# Ricky Bobby?

1. Feb 27, 2009

### ldbaseball16

Ricky Bobby??

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

Ricky Bobby jumps into his 1003kg pick up and heads out at 69.2mi/h. It's night and he notices too late the warning sign that the bridge is out. He slams on the brakes and skids for 45.2(kinetic friction=0.78)before hitting the long massive coil spring that is rigidly mounted onto the barricade. In addition to his skidding tires, the spring brings him to a stop. The spring constant is 3.57 x 10^4 N/m. how far does he travel after making contact with spring???

2. Relevant equations
1/2mv^2+1/2Kx^2=1/2mv^2+1/2kx^2 ?????????????????// im not sure if this is the right equation i dont think it is ive looked everywhere in my book to find a relevent equation i was wondering if anyone can point me towards the right equation please

3. The attempt at a solution

refer to (b)2.

2. Feb 28, 2009

### tiny-tim

Hi ldbaseball16!

Is that 45.2 feet?

This is an energy problem …

so yes, that equation is right, but you also need to use the work-energy theorem … work done by friction = loss of mechanical energy

3. Feb 28, 2009

### ldbaseball16

Re: Ricky Bobby??

ok Wnet=(1/2)mv^2-(1/2)mv^2 this is the work energy theorem but on the other equation i have to apply the kinetic friction to 45.2m???? right and once i find the conservation of mechanical energy what do i do with that number???? how do i apply it to the work-energy theorem???

Last edited: Feb 28, 2009
4. Feb 28, 2009

### tiny-tim

uhh? too cryptic

just do it!