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 pebbles Oct15-07 08:12 PM

How to find the maximum acceleration given coefficient of static friction and mass

1. The problem statement, all variables and given/known data
A flatbed truck is carrying a 20.0-kg crate along a level road. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum acceleration that the truck can have if the crate is to stay in place?

2. Relevant equations
Is the equation to solve for maximum acceleration F s,max= usN * us?

3. The attempt at a solution
I was not taught how to do problems like this...not 100% sure what to plug in for usN...I gave it a shot:
The surface is flat, so I guess the normal force=20.0 kg, so I then mulitplied by .40 to get 8 m/s.........ahhhh. I don't know what I'm doing!

 PhanthomJay Oct15-07 08:38 PM

Quote:
 Quote by pebbles (Post 1467904) 1. The problem statement, all variables and given/known data A flatbed truck is carrying a 20.0-kg crate along a level road. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum acceleration that the truck can have if the crate is to stay in place? 2. Relevant equations Is the equation to solve for maximum acceleration F s,max= usN * us?
Fsmax = usN. Then use Newton's 2nd law.
Quote:
 3. The attempt at a solution I was not taught how to do problems like this...not 100% sure what to plug in for usN...I gave it a shot: The surface is flat, so I guess the normal force=20.0 kg, so I then mulitplied by .40 to get 8 m/s.........ahhhh. I don't know what I'm doing!
20 Kg, is the mass, the normal force is its weight. Use formula that relates weight with mass.

 pebbles Oct15-07 08:51 PM

Quote:
 Quote by PhanthomJay (Post 1467934) 20 Kg, is the mass, the normal force is its weight. Use formula that relates weight with mass.
uh, hmm. I looked through my notes, couldn't find this kind of formula.

What am I to do to solve this problem? I looked at the F s, max formula wrong, so it's us times N. I was initially puzzled by usN times us. Now it makes since.

So, us= .40 right? But I don't know how to get the weight of 20kg for normal force, N.

Thanks

 PhanthomJay Oct15-07 09:28 PM

The normal force on the crate, in this problem, is equal to the weight, since there is no acceleration vertically and only the weight and normal forces act in the vertical diretion, so they must be equal and opposite in satisfaction of newton's 1st law. Now weight is just the force caused by the acceleration of gravity, please memorize it, W=mg, where g is the acceleration of gravity where g is equal to 9.8m/s/s on the earth's surface. When the mass is in kilograms, the weight, using this formula, is in newtons. 20 Kilograms weighs 196 newtons.

 pebbles Oct15-07 10:49 PM

so my answer will be .40 times 196 N which is 78 m/s^2?!

 ajanthan14 Jul15-11 01:14 AM

Re: How to find the maximum acceleration given coefficient of static friction and mas

A flatbed truck is carrying a 20.0-kg crate along a level road. The coefficient of static friction between the crate and the bed is 0.400. What is the maximum acceleration that the truck can have if the crate is to stay in place?

f=ma for (m) moving direction
R=ma
F=mg
coeffi.fric=F/R=mg/ma
a=g/coeff.fri
= 10/0.4m/s2
=25m/s2

 trucker3290 Dec7-11 09:59 PM

Re: How to find the maximum acceleration given coefficient of static friction and mas

I love this problem and since I am a flatbed driver I have a more interesting one:

48 feet flatbed