Find the mass of object knowing the applied force and coefficient of friction

[liz777]

Homework Statement

If a force of 45 Newtons is needed to overcome friction and the coefficient of friction=0.26, what is the mass of the object?

The Attempt at a Solution

So would I need to find the frictional force first? But then I can't use the equation: (frictional force=coefficient of friction x weight) since I don't have the mass. I also thought about using the equation F=MA but then I don't have the acceleration, the friction, or the net force! Any help, I'm really stuck?

 

[Doc Al]

So would I need to find the frictional force first?

They give you the friction force. The way to interpret the given information is that the 45 N force is just enough to overcome friction, thus that force equals the friction.

But then I can't use the equation: (frictional force=coefficient of friction x weight) since I don't have the mass.

Sure you can use that equation. Remember that you're asked to find the mass.

 

[liz777]

Ok, so what you're saying is that the applied force equals the friction, in this case. I thought it wouldn't move though if that was true? I'm just confused on this concept.

But anyway, using that information, frictional force=coefficient of friction x weight
45=0.26m(9.8)
45=2.55m
m=17.65kg
Is that right?

 

[Assasinof6]

Yes.
You are given two values, and you need to solve for one of them using an equation with four variables, three of which are known (the other being g).