# Homework Help: Find centre of mass

1. Jan 29, 2017

### Kajan thana

1. The problem statement, all variables and given/known data
The lamina is free to rotate about a fixed smooth horizontal axis, perpendicular to the plane of the lamina, passing through the point A. and hangs in equilibrium.
Find the angle between AC and the horizontal.

I have attached a the solution to the question, it seems like there is no line to the question and theta there are showing in the working out.

2. Relevant equations
I think the answer is 9.46 degree as tanφ= 1/6

3. The attempt at a solution.
I have attached screenshot to this thread. Is the solution wrong or have I been thinking in a wrong way? What are looking at that theta shown in the screenshot?

#### Attached Files:

• ###### Screen Shot 2017-01-29 at 22.21.04.png
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Last edited by a moderator: Jan 29, 2017
2. Jan 29, 2017

### Nidum

More like thinking upside down . If you were holding the lamina in the position shown what would happen when you let go of it ?

3. Jan 29, 2017

### Kajan thana

lamina will turn so the centre of mass is below the pivot.

4. Jan 29, 2017

### Nidum

That's it .

5. Jan 29, 2017

### Kajan thana

yes but my question why have they goy theata there when they ask for the theta between the horizontal and AC

Last edited: Jan 29, 2017
6. Jan 29, 2017

### Kajan thana

i thought about it. It makes sense what they have done.