Finding length of skid marks using f k

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Homework Help Overview

The problem involves calculating the length of skid marks left by a car that skids to a halt on wet concrete. The scenario includes a 1000 kg car traveling at a speed of 40 m/s and a coefficient of kinetic friction of 0.60.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to calculate the length of the skid marks using the frictional force and expresses uncertainty about the next steps after calculating the frictional force. They consider using a formula related to distance but are unsure.
  • Some participants suggest finding acceleration from the frictional force and applying standard equations of motion.
  • There is a moment of self-doubt from the original poster regarding their understanding of the relationship between friction force and acceleration, which they later clarify.

Discussion Status

The discussion is active, with participants providing guidance on how to proceed from the calculated frictional force to finding acceleration. There is a recognition of the need to apply Newton's second law, indicating a productive direction in the conversation.

Contextual Notes

Participants are navigating the relationships between forces, acceleration, and distance in the context of a physics problem, with some initial confusion about the connections between these concepts.

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Finding length of skid marks using fk

Homework Statement



A 1000kg car traveling at a speed of 40m/s skids to a halt on wet concrete where µk = 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



Fg = mg = weight = normal force

fk = µkFN

The Attempt at a Solution



Fg = 1000(9.8) = 9800 N, therefore the normal force = 9800N
µk = .60

fk = .60(9800)
fk = 5800 N

v0 = 40m/s
fk = 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
 
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Welcome to PF!

Hi physjeff12! Welcome to PF! :wink:
physjeff12 said:
fk = 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 fk, find the acceleration, and then use one of the standard constant acceleration equations. :smile:
 


tiny-tim said:
Hi physjeff12! Welcome to PF! :wink:From fk, find the acceleration, and then use one of the standard constant acceleration equations. :smile:

thanks :smile:

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

EDIT: nvm, i am stupid. i found out how. F = ma :smile:
 
Friction is like any other force …

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

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