When the truck is at rest, will the crate also be at rest?

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Homework Help Overview

The discussion revolves around a physics problem involving a crate on a truck, specifically examining whether the crate remains at rest when the truck is at rest or if it will slide downwards. The subject area includes concepts of forces, friction, and static equilibrium.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the normal force acting on the crate and the calculations related to maximum and minimum friction forces. There are questions about the necessity of calculating the minimum friction force if the crate is assumed to be at rest. Some participants clarify terms and notation used in the equations.

Discussion Status

The discussion is ongoing, with participants providing clarifications and affirmations regarding the calculations. There is acknowledgment that the crate can be assumed to be placed statically until static friction is overcome. Some participants express curiosity about additional parts of the problem that may exist.

Contextual Notes

There are indications of potential confusion regarding the definitions of static and kinetic friction, as well as the notation used in the equations. The original poster mentions that there are more parts to the problem that they are currently trying to solve.

javii
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Homework Statement


I have attached the known information.
problem-2-png.113891.png

When the truck is at rest, will the crate also be at rest or will it slide
downwards?

Homework Equations


Sum F_y =0
G_max = (my_s)*N
G_min = (my_k) * N

The Attempt at a Solution


I did a Free body diagram on the crate (see the attached file)

The first step is finding the normal force.
Sum F_y =m*a_y =0
N-mg*cos(10)=1932.19 N

now i find the friction forces
G_ max=(my_s)*N= 0.70*1932.19=1352.53 N
G_min=(my_k)*N=0.50*1932.19=966.10 N

Now i will find F_II
F_II = m*g*sin(10) = 340.70 N

since G_max > F_II there is no motion downwards i,e a_x = 0

I am not sure if I have done it correct.
Thank you for your help.
 

Attachments

  • problem 2.PNG
    problem 2.PNG
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javii said:
N-mg*cos(10)=1932.19 N
I assume you mean N=mg*cos(10)=1932.19 N
javii said:
G_min = (my_k) * N
Only if it is moving. And it is mu, not my.
You can get the actual Greek character and subscript using the buttons just above the text area, Σ, X2, X2
javii said:
since G_max > F_II there is no motion downwards
Yes.
 
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haruspex said:
I assume you mean N=mg*cos(10)=1932.19 N

Only if it is moving. And it is mu, not my.
You can get the actual Greek character and subscript using the buttons just above the text area, Σ, X2, X2

Yes.
Yes i ment N=mg*cos(10)=1932.19 N (isolating for N)

So I don't have to calculate for G_min? Meaning I can skip this part in the calculations?
 
javii said:
Yes i ment N=mg*cos(10)=1932.19 N (isolating for N)

So I don't have to calculate for G_min? Meaning I can skip this part in the calculations?
Yes. You can assume the crate was placed statically. Until static friction is overcome, it is going nowhere.
I would have guessed there are more parts to the problem.
 
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haruspex said:
Yes. You can assume the crate was placed statically. Until static friction is overcome, it is going nowhere.
I would have guessed there are more parts to the problem.
haruspex said:
Yes. You can assume the crate was placed statically. Until static friction is overcome, it is going nowhere.
I would have guessed there are more parts to the problem.
Okay. Thank you very much. And yes there are more parts to the problem, i am trying to solve them now.
 

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