# Coefficient Of Static Friction

I'm sure that this is a very simple question, but I can't find it in my text. I made a few attempts but I see why they're incorrect, I just can't figure out the correct method.

## Homework Statement

A flatbed truck is carrying a 60.0 kg crate along a level road. The coefficient of static friction between the crate and the bed is 0.490. What is the magnitude of the maximum acceleration that the truck can have if the crate is to stay in place?

I used N-mg=may.

## The Attempt at a Solution

N=mg
0.490/60 = 0.008 ( I see why this is incorrect).

and

N=mg=(60)(-9.81)=-588.6 N (I think that I have to use this somehow).

Thanks!

tiny-tim
Homework Helper
Hi kaylanp01! (have a mu: µ )

Hint: ignore m … the m's all cancel … the acceleration is the same for any object with the same µ. Hi kaylanp01! (have a mu: µ )

Hint: ignore m … the m's all cancel … the acceleration is the same for any object with the same µ. I still don't understand. Do I need to introduce a new formula? Or do I have everything that I need there already?

Thanks for the µ :).

tiny-tim
Homework Helper
Hi kaylanp01! I still don't understand. Do I need to introduce a new formula? Or do I have everything that I need there already?

Thanks for the µ :).

erm … well, you need a formula involving µ, for a start! Hi kaylanp01! erm … well, you need a formula involving µ, for a start! haha hey now, be nice. its a saturday night and i'm doing a physics capa, how good is my mindset supposed to be right now? :P

the only formula that I can find with µ is the one for kinetic friction, but i can't see how thats significant. am i missing something?

tiny-tim
Homework Helper
haha hey now, be nice. its a saturday night and i'm doing a physics capa, how good is my mindset supposed to be right now? :P

wot's a capa? the only formula that I can find with µ is the one for kinetic friction, but i can't see how thats significant. am i missing something?

mmm … how about an equation relating normal force to static friction? (or, to put it another way, what is the coefficient of friction?)

wot's a capa? mmm … how about an equation relating normal force to static friction? (or, to put it another way, what is the coefficient of friction?)

a capa is hell in the form of an online assignment. haha.

okay, i have the formula that you're talking about, i think...and i assume that it gives you
fs(max)= µsN=0.490(-588.6)=288.4

fs=ma
-288.4=(60)a
a=-4.81 m/s^2=4.81 m/s^2

now i shall insert that answer andddd...
correct!

thank you thank you! :)

tiny-tim
Homework Helper
okay, i have the formula that you're talking about, i think...and i assume that it gives you
fs(max)= µsN=0.490(-588.6)=288.4

fs=ma
-288.4=(60)a
a=-4.81 m/s^2=4.81 m/s^2

now i shall insert that answer andddd...
correct! Woohoo! … though you would get even more marks if you didn't put those m's in.  Woohoo! … though you would get even more marks if you didn't put those m's in. the sad part about a capa is that every question is only worth 1 mark :(, but i will keep that in mind for my exam :).