Magnitude of the Force of friction

[RubenL]

Homework Statement

A child pulls a wagon at a constant velocity along
a level sidewalk. The child does this by applying a
22-Newton force to the wagon handle, which is inclined at 35° to the sidewalk.

What is the magnitude of the force of friction on the
wagon?

Homework Equations

Ff = µFn

The Attempt at a Solution

I do not understand this question...if they are asking for the force of friction, shouldn't the question include the mass as well as the coefficient of friction??

The only attempt to the question i can make is figuring out the X and Y component of force. (however i do not think the X component is needed here, so i will only do the Y)

Y = (Sin35)22 = 13N
is this the correct answer? (force of friction...?)

 

[Dewgale]

On the contrary, the Y-component of the force is unnecessary.

Think about what you know about the force of friction, and keep in mind that, since the wagon is going at a constant velocity, all of the forces must be balanced. If the forces are balanced, F_f must equal another force.

Do you know which it is?

 

[RubenL]

Well that was an easy one...

Constant velocity = 0 acceleration, thus no unbalanced forces;

Fx = (cos35)(22) = 18N

Therefore, the magnitude of the Ff must be = 18N.

Thank you!

 

[Dewgale]

You're very welcome! :)