Calculate the friction between sticks and the ceiling/floor

[Jorgen1224]

Homework Statement

There is a metal stick that is connected to the ceiling with another one. The angle between them is 60°. Calculate the friction.

Both lengths and weights are the same.

Homework Equations

T = f N
or actually none, except trygonometry

The Attempt at a Solution

I tried using this equation T = f N and convert it somehow, but i bet that trygonometry is strictly required here, but i don't really know how to use it. So I'm asking for any tips that could help me out.

I see that if we cut this structure in a half then we have 2 equal rectangular triangles with angles: 30, 60 and 90. And i don't really know what am i supposed to do next

Sorry for inaccuracies, because scientific english is quite new for me.
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Actually i made a new thread, because in the last one i made a huge mistake, i simply meant friction but I wrote tension Sorry for those who attempted at my problem and tried to understand what i meant.

 

[CWatters]

The problem statement doesn't make sense to me. Can you post it exactly as written.

Can you mark on the drawing which way gravity is acting.

 

[Jorgen1224]

It's something that was told to me, but i'll try to explain it better.

There are 2 metal bars as shown on the picture, the angle between them is 60°. We're supposed to calculate minimum coefficient of friction so that this is possible.
Their lenghts and weights are the same.

 

[CWatters]

I don't think you can solve this. There is not enough information to calculate the force that the top bar puts on the ceiling.

It depends on:

1)The vertical distance between the open ends of the bars.
2)The vertical distance between floor and ceiling.

2) must be less than 1).

3)The thickness of the bars. They create a force on the ceiling by bending.

 

[CWatters]

Can I check... Are the two bars are welded together where they join at 60 degrees?

 

[Jorgen1224]

Yes, they are

 

[Jorgen1224]

And just to be clear actually the force we're supposed to find is the bottom one. Top one is connected to the ceiling, but the bottom one is not. Sorry if i said something wrong or forgot to mention something.

 

[haruspex]

Yes, they are

As CWatters notes, if they are welded together there is no limit to the normal force, so no way to solve the problem.
As I wrote on the previous instance of this thread, I would assume the top rod is freely jointed at each end. And as I also wrote there, draw a free body diagram for each rod, write out the forces acting on each, and the usual statics equations relating them.

 

[Jorgen1224]

Okay, thanks, i'll make an attempt.

And also this problem could be put in other words: What minimum coefficient of friction must be present so the structure doesn't slide (to the left)

Anyway if there was indeed a mistake in what i said before or something like that i am going to post here a solution to this problem after i ask my teacher about it tomorrow.

 

[CWatters]

+1

I agree with all of that.

 

[Jorgen1224]

Okay i was just told that the angle can change... That indeed changes a lot