# Homework Help: Mechanics statics problem

1. Apr 21, 2012

### matematikuvol

1. The problem statement, all variables and given/known data
Homogeneous cube with one edge lying on the floor and the other on a smooth vertical wall. The underside of cube with a horizontal surface makes angle of $$\frac{\pi}{6}$$.What is the value to the coefficient of friction between the cube and the floor to cube remain in balance.

2. Relevant equations
$$\sum F=0$$
$$\sum M=0$$
$$M=rF$$
M is momentum of force.

3. The attempt at a solution
In static case

$$\sum F=0$$
$$\sum M=0$$
I need help to write this equation from the problem statement. I don't have idea.
Because cube is homogenuous the forces are equal from all parts I suppose.

My assymption is that $$r$$ is size of cube so $$a$$. Do you have any idea? I think this goes in one line but it is hard for me.

Last edited: Apr 22, 2012
2. Apr 22, 2012

### matematikuvol

Any help?

I think that this is picture

Last edited: Apr 22, 2012
3. Apr 22, 2012

### matematikuvol

Here is a picture

#### Attached Files:

• ###### cube.JPG
File size:
3.4 KB
Views:
105
4. Apr 23, 2012

### matematikuvol

How to define $$\sum M=0$$?

5. Apr 23, 2012

### Whovian

Um ... momentum of force ... ?

If $\displaystyle M=r\cdot F$, then $\displaystyle\sum\left(M\right)=r\cdot\sum\left(F \right)$, and so, as r≠0, $\displaystyle\sum\left(F\right)=0$, which we already knew. That's the equivalent of just no net force being applied.

6. Apr 23, 2012

### matematikuvol

I mean in this case.