Force and Newtons law of motion

[pat666]

Homework Statement

your car rolls on a level street at 50km/h. the coefficient of kinetic friction is 0.023. how far will the car go before stopping. (no breaking.)

Homework Equations

The Attempt at a Solution

F_fric=0.226m
F_a=(-1250/s)*m
i need to make F_a-F_fric equal to something to solve for s, the m's will cancel. I have no idea what it will equal since its not in equilibrium...

 

[tiny-tim]

hi pat666!

use work done and the work-energy theorem

 

[pat666]

kk ill give that a whirl and tell you if i still can't do it... thanks

 

[pat666]

Hey, i still can't get this i tried finding the net work which i got -1250m J and then W=F/x with F=(-1250m)/x-0.226m. i got the acceleration (for F=ma) using kinematic equations.?

 

[tiny-tim]

Hey, i still can't get this i tried finding the net work which i got -1250m J and then W=F/x with F=(-1250m)/x-0.226m. i got the acceleration (for F=ma) using kinematic equations.?

Sorry, I don't understand any of that.

What is the energy? what is the force ?

If the distance is d, what is the work done ?

 

[pat666]

I just found the net work using 1/2mv^2-1/2mu^2. then i used W=F/x, to find the Force i just found the Force from friction and the "applied force". I might be doing something completely wrong, could you give me some more detailed instructions please.

 

[ideasrule]

It's W=Fx, not W=F/x. Also, there's no applied force; the force on the car is just the force of friction.

 

[pat666]

ok that's where i screwed up. thanks...