Mechanics -- Object sliding again with friction

[prehisto]

Homework Statement

first of all- yes,i looked into similar topics,did not succeed :(

My problem : The objects slides down on a plane which located 45degrees with respect to surface. It slides s=0.36m down, it reaches v=2m/s. I have to calculate the coefficient of friction.

Homework Equations

The Attempt at a Solution

There is image( sorry for some reason, i could not upload it directly to here)
[/B]
http://postimg.org/image/uof2i65zv/

So the friction coef. F_friction=(mu)*F_reaction -> (mu)=F_f/F_r
From image above, its easy to see,that tan(alpha)=mu,so it seems too easy.

And what for i need s and v values? I suppose it could be because i just calculated the static friction ,not the dynamic,yes? If i should calculate the dynamic one,could someone help ,please?

 

[NTW]

I think that you should start with a clear sketch of the inclined plane, with the sliding object and the forces involved... I've seen your image, and it doesn't seem clear to me...

 

[prehisto]

I think that you should start with a clear sketch of the inclined plane, with the sliding object and the forces involved... I've seen your image, and it doesn't seem clear to me...

I can't imagine what can i ad, there is Force of friction,reaction and mg, corresponding counter forces..

 

[NTW]

The essential vectors that you should draw clearly are:

1) The weight mg
2) One of its components, normal to the plane
3) The other component, parallel to the plane
4) The friction force.

 

[prehisto]

The essential vectors that you should draw clearly are:

1) The weight mg
2) One of its components, normal to the plane
3) The other component, parallel to the plane
4) The friction force.

http://postimg.org/image/6ztyvaf4r/

F_F is the friction force.
And now there is components of mg!

 

[NTW]

You should list those forces, one by one, as functions of mg. Then, write down the expression of the net force along the plane.

After that, you should ask yourself: does the object accelerate in his sliding motion? And by how much?

There may be other approaches to the problem, of course. That's just my way of solving it, that I believe correct...