# Euilibrium of a deformable body

1. Jun 29, 2009

### x850xtpe

Here are more unknows need to slove while I had only two equations which are sum of force on y-asix = 0 and sum of moment = 0. It is out of my learn. How can I solve these unknows?

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2. Jun 29, 2009

### viola.geek

Not sure what you mean by "sum of moment = 0," but for equilibrium problems, I know you need to sum the forces in the x and y directions, sum the torques in the x and y directions, and set them equal to zero as you said, since everything is in equilibrium. Solve for your unknowns.

3. Jun 29, 2009

### x850xtpe

The moment which is cause the body to rotate, like torque.
Althought I had built the 2 equations, sum of moments = 0, sum of forces acting on y-asix = 0, I still cannot slove these unknows. I had not set the equation sum of forces acting on x axis, it is because no forces action on x-asix in this case. It is particular problem...

4. Jun 29, 2009

### viola.geek

Could you post your work on it thus far? That might make it a bit easier to see what you have.

Also, are you accounting for the direction of each? (Such as a force acting downward being negative, while a force acting upwards being positive? Depending on your axes.)

5. Jun 29, 2009

### x850xtpe

ok...........................

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6. Jun 29, 2009

### viola.geek

I did a quick Google search and found this site: http://www.public.iastate.edu/~fanous/ce332/force/cdmoment.html
Perhaps that will be of some help.

Also, what happened to your first equation? It looks like it simplifies to
100 - 3VB + MA + MB = 0

Are MA or MB at all related to VB and VA (or the forces and the distance away from them)? Maybe you can get an expression for VB in terms of MA or MB.

7. Jun 29, 2009

### BobbyBear

Your beam is statically indeterminate, which means that you cannot obtain the reactions by simply applying the static equilibrium equations (note that you have four unknowns and only two static equilirbrium equations, eg. one moment equation and one force equation in the vertical direction).

You must use elastic equilibrium equations as well to solve.

8. Jul 4, 2009

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