# Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semester

1. Sep 17, 2010

### snshusat161

1. The problem statement, all variables and given/known data
A uniform bar AB of length l and weight W is hinged to the wall at its end A and supported by means of a string of length a which is tied to the wall as shown. Find the angle $$\theta$$ that the bar will make with the wall corresponding to the position of equilibrium

2. Relevant equations
Moment = Force X perpendicular distance

3. The attempt at a solution

I had tried to find moment about point A. I had resolved W and T (tension in the string BC) into rectangular components. One along the bar and other perpendicular to the bar. along the bar components will not add to the moments at A while the perpendicular components will get multiplied by the distance (For T and W, l and l/2 respectively) and added according to sign convention (anticlock wise rotation as positive and clockwise rotation as negative). but because the angle ABC is getting too bulky (complicated), I don't think I can anyhow end this problem with answer. Need your immediate help.

2. Sep 17, 2010

### snshusat161

Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

W acts from the center of the bar.

angle A = $$\theta$$

3. Sep 17, 2010

### pongo38

Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

Are you sure there isn't another bit of information?

4. Sep 17, 2010

### snshusat161

Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

very sure!

5. Sep 17, 2010

### zhermes

Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

There isn't enough information to solve the problem. You need to know where 'C' is.

6. Sep 17, 2010

### pongo38

Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

In the diagram attached (I hope it does) it shows the 3 forces W RA and RC meeting at the midpoint of the string. The two triangles (G for geometry, and F for forces) should be similar, and there should be enough information to conclude all the dimensions and forces. The only dimension not shown is the horizontal projection of the G triangle, and that is L/2*(cos theta). But there still is not enough information to bring this to completion.

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Last edited: Sep 18, 2010
7. Dec 2, 2011

### MIGOM PEGU

Re: Engineering Mechanics (Chapter: General Case of Force in a Plane) of First Semest

I want the solutions of all the problem i.e in this chapter. So please help me in solving the problem of this chapter...