What is the magnitude of the frictional force?

[soul5]

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?

 

[LowlyPion]

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.

 

[Dr.D]

What direction is the 200 N applied to the crate?

 

[soul5]

What direction is the 200 N applied to the crate?

strictly horizontal why do you ask?

 

[LowlyPion]

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.