Finding length of skid marks using f k

[physjeff12]

Finding length of skid marks using f_k

Homework Statement

A 1000kg car traveling at a speed of 40m/s skids to a halt on wet concrete where µ_k = 0.60. How long are the skid marks?

(i know this an easy problem, but i am stuck when trying to find the length of the skid marks.)

Homework Equations

F_g = mg = weight = normal force

f_k = µ_kF_N

The Attempt at a Solution

F_g = 1000(9.8) = 9800 N, therefore the normal force = 9800N
µ_k = .60

f_k = .60(9800)
f_k = 5800 N

v₀ = 40m/s
f_k = 5880 N

Where do i go from here to find the distance of the skid marks?

i was thinking maybe using the formula, x = x₀ + vt, but i am not sure

 

[tiny-tim]

Welcome to PF!

Hi physjeff12! Welcome to PF!

f_k = 5880 N

Where do i go from here to find the distance of the skid marks?

i was thinking maybe using the formula, x = x₀ + vt, but i am not sure

From f_k, find the acceleration, and then use one of the standard constant acceleration equations.

 

[physjeff12]

Hi physjeff12! Welcome to PF! From f_k, find the acceleration, and then use one of the standard constant acceleration equations.

thanks

and how do i find the acceleration using f_k? i don't know any formulas that connect acceleration with friction force.

EDIT: nvm, i am stupid. i found out how. F = ma

 

[tiny-tim]

Friction is like any other force …

just use good ol' Newton's second law. ​