How to use friction equations

[HelloImAsh]

Homework Statement

The coefficient of sliding friction between two materials is 0.35. A 5.0 kg object made of one material is being pulled along a table made of another material. What is the force of friction?

I'm fairly certain I solved the problem correctly, the thing is, I should be getting a negative force as the answer (because I defined forward as positive), and I'm getting a positive force. Could someone please point out which part of my solution is incorrect.

Homework Equations

F1 is force of sliding friction, F2 is normal force, and μ is the coefficient of sliding friction:
F1=μF2

The Attempt at a Solution

F1=μF2
=0.35(mg)
=17.15N

 

[SammyS]

Homework Statement

The coefficient of sliding friction between two materials is 0.35. A 5.0 kg object made of one material is being pulled along a table made of another material. What is the force of friction?

I'm fairly certain I solved the problem correctly, the thing is, I should be getting a negative force as the answer (because I defined forward as positive), and I'm getting a positive force. Could someone please point out which part of my solution is incorrect.

Homework Equations

F1 is force of sliding friction, F2 is normal force, and μ is the coefficient of sliding friction:
F1=μF2

The Attempt at a Solution

F1=μF2
=0.35(mg)
=17.15N

The equation F₁=μF₂ only gives the magnitude of the frictional force. The force of friction, F₁, is in a direction perpendicular to the normal force, F₂ , so that equation cannot be true in a vector sense.

The force of friction is in such a direction as to oppose the relative motion of the two objects.