Applying Newton's Laws to Friction: Solving Homework Problems

[Fatima Hasan]

Homework Statement

Homework Equations

F = ma
Fr = uK * N

The Attempt at a Solution

My answer is 7 but it is not one of the choices

Thanks in advance[/B]

 

[jbriggs444]

In what direction will the force of kinetic friction act? Don't you have to figure that out before you can determine its components?

Edit: Note that you may be better off starting differently. What is the magnitude of the force from F₁ and F₂ combined?

 

[jbriggs444]

F1 = 5 N
F2 = 20N

That does not answer the question.

Let me ask it another way: "Ignoring friction, what is the magnitude of the total force acting on the object?"

 

[Fatima Hasan]

That does not answer the question.

Let me ask it another way: "Ignoring friction, what is the magnitude of the total force acting on the object?"

to the +ve x-axis
so friction is -ve x-axis

 

[Fatima Hasan]

Fx = F1cos37+F2cos37=20 N

 

[jbriggs444]

Fx = F1cos37+F2cos37=20 N

What is the magnitude of the total of the two forces? Not just the X component.

Oh... As I understand the problem, we are looking down at the surface of a table from above. Your understanding is that we are looking from the side with one force pulling diagonally up and one pulling diagonally down?

 

[Fatima Hasan]

What is the magnitude of the total of the two forces? Not just the X component.

Oh... As I understand the problem, we are looking down at the surface of a table from above. Your understanding is that we are looking from the side with one force pulling diagonally up and one pulling diagonally down?

yes

Tried your thought, got wrong answer too

 

[jbriggs444]

The "looking down from above" interpretation yields an answer that matches one of the choices.

 

[Fatima Hasan]

The "looking down from above" interpretation yields an answer that matches one of the choices.

Thanks.Got it . It's choice C