Coefficient of Friction and Forces

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Homework Help Overview

The discussion revolves around a problem involving the coefficient of friction between a box and the bed of a flatbed tractor trailer. The scenario includes the truck accelerating from a stop and the box sliding backward, prompting questions about the necessary formulas and variables to determine the coefficient of friction.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the relevant formulas for friction and forces, questioning the absence of mass and acceleration in the given problem. There is an exploration of how to derive acceleration from known values and how to find the normal force without mass.

Discussion Status

Some participants have made progress in calculating acceleration but express uncertainty about how to proceed without knowing the mass. Suggestions have been made to consider the cancellation of mass in equations, indicating a collaborative effort to explore the problem further.

Contextual Notes

The problem lacks specific values for mass and force, which are critical for applying the formulas correctly. Participants are also navigating the constraints of the homework context, which may limit the information they can assume or use.

pippintook
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A flatbed tractor trailer takes off from a stop sign on a level road. If a box on the back slides back 10 meters while the truck goes forward 50 meters and attains a speed of 15 m/s, what is the coefficient of friction (μ) between the bed and the box? Assume the bed to be at least 10 meters long.


FF= μFN
FN= mg


I don't know if those are the right formulas, specifically because no mass is given. I just don't know how to find the forces without acceleration; is there a formula for that? If these are the right formulas, how do I find the mass or FN? I chose these formulas because FF is the forward force, and it had μ in the equation. Help!
 
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That's some of them.

There is also F = m*a.

And that a would be really useful to know wouldn't it?

You know the final velocity and you know the distance, so you should be able to figure the "a" shouldn't you?
 
Wow. Ok, so I've found "a", but still don't know how to get FN, since I don't have the mass or force. I know there's some really obvious formula, but I CANNOT remember it.
 
pippintook said:
Wow. Ok, so I've found "a", but still don't know how to get FN, since I don't have the mass or force. I know there's some really obvious formula, but I CANNOT remember it.

Maybe write out your equations and your mass will cancel out?

If you are looking for kinematic equations:
https://www.physicsforums.com/showpost.php?p=905663&postcount=2
 
Last edited:

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