What is the magnitude of the frictional force?

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Homework Help Overview

The discussion revolves around determining the magnitude of the frictional force acting on a crate being pushed with a specified force. The context includes the mass of the crate, the coefficient of kinetic friction, and the applied force.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore the calculation of the frictional force using the equation Ff = uN, questioning the role of the applied force and its direction. There is discussion about how different applied forces might affect the frictional force.

Discussion Status

The discussion is active, with participants raising questions about the implications of the applied force's direction and magnitude on the frictional force. Some guidance is provided regarding the need to consider the normal force in cases where the applied force is not strictly horizontal.

Contextual Notes

Participants note that the applied force's direction and magnitude could influence the normal force and, consequently, the frictional force. There is an emphasis on the need to clarify assumptions regarding the force's direction.

soul5
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Homework Statement



A person pushes with force of 220N on a 40 kg create. The coefficient of kinetic friction of 0.35. What is the magnitude of the frictional force?



Homework Equations




Ff = uN


The Attempt at a Solution




so do I just go

Ff = 0.35*(40kg)(9.81m/s^2)


Is that it?


What is the 220 Force for?
 
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soul5 said:

Homework Statement



A person pushes with force of 220N on a 40 kg create. The coefficient of kinetic friction of 0.35. What is the magnitude of the frictional force?

Homework Equations


Ff = uN

The Attempt at a Solution


so do I just go

Ff = 0.35*(40kg)(9.81m/s^2)

Is that it?
What is the 220 Force for?

As stated it seems to be. But what if the force had been just 100N? The frictional force would only have been 100N then wouldn't it? The point is that the crate is being pushed with sufficient force to involve kinetic friction.

Now if the force is not strictly horizontal, then there is the additional normal component that would also need to be taken into account to determine the frictional force.
 


What direction is the 200 N applied to the crate?
 


Dr.D said:
What direction is the 200 N applied to the crate?

strictly horizontal why do you ask?
 


Any angle would mean that there would be an additional normal force that would need to be accounted for. It would be the normal component of the force that would then be added to its weight and multiplied by μ.
 

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