Max Acceleration of a 20.0kg Crate on a Flatbed Truck

[pebbles]

Homework Statement

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?

Homework Equations

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

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!

Thanks in advance.

 

[PhanthomJay]

Homework Statement

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?

Homework Equations

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

Fsmax = usN. Then use Newton's 2nd law.

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]

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]

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]

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

 

[ajanthan14]

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]

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

48 feet flatbed
6000 pounds load 8 feet high (the load is full trailer)
A flatbed is 8.5 feet whide
driver will drive at 65 miles per hour (there is no wind)

How many straps and how tiht should they be so he does not lose everything in 600 miles :D

(I'm a geek flatbed driver... If I get an answer to this I will post more)