Solving a Statics Problem: Where Do I Start?

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In summary: Statics problemi have been working on this problem now for 2 hours and haven't gotten anywhere,taking the moment around joint a or b still leaves you with 2 unsolved equations. and suming the forces leaves with 2 also can anyone point me in the right direction, i just need to determine the reactions at a, and b i have drawn a Free body diagram. thanksIn summary, the statics problem is difficult and requires more than just equilibrium equations. You need to use the equations to determine the reactions at a and b, and then combine them.
  • #1
tufftrav
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Statics problem

i have been working on this problem now for 2 hours and haven't gotten anywhere,
taking the moment around joint a or b still leaves you with 2 unsolved equations. and suming the forces leaves with 2 also can anyone point me in the right direction, i just need to determine the reactions at a, and b i have drawn a Free body diagram. thanks

http://img255.imageshack.us/my.php?image=staticsum4.png"
 
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  • #2
the length from a to b is 8' and 6' from b-e I am sorry i didn't put that in my drawing
 
  • #3
Welcome to PF!

tufftrav said:
the length from a to b is 8' and 6' from b-e I am sorry i didn't put that in my drawing

Hi tufftrav! Welcome to PF! :smile:

(This is the same question as in thread https://www.physicsforums.com/showthread.php?t=224637, isn't it?)

Can you please clarify:

Is the whole thing on a fixed pivot at the centre, E?

What is the force at C (also called E)?

Are A and B resting on the ground (you've called them "joints"), or what? :smile:
 
  • #4
yea i double posted, the only pivot is at c, the is a force at e 100#, and force at d 100#, points a, and b were pin joints.
 
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  • #5
I've always found these frame problems difficult. You have to use more than the equilibrium equationss when you have more unknowns than the number of those equations. The equilibrium equations will give you the y values of the reactions at a and b, but not the x values, which must exist at both these supports for stability. I think I would look at the recations due to each applied force separately, then combine them in the end to get the total reactions. When you look at them separately this way, you can identify which of the 2 members is a so called '2 force' member for that load, that is, it is not subject to shear, and has axial load only (internal bending moments in a member at pins cannot transfer at those pins to other members).
 

1. How do I approach a statics problem?

To solve a statics problem, you must first understand the given problem and identify the knowns and unknowns. Then, draw a free body diagram of the system and apply the equations of equilibrium to solve for the unknowns.

2. What are the equations of equilibrium?

The equations of equilibrium are the sum of forces in the x-direction, sum of forces in the y-direction, and sum of moments about a point. These equations state that for a system to be in equilibrium, the net force and net moment must equal zero.

3. How do I determine the direction and magnitude of forces in a statics problem?

To determine the direction of forces, you can use vector analysis and trigonometry. The magnitude of forces can be found by using the equations of equilibrium and solving for the unknowns.

4. What are the key principles to remember when solving a statics problem?

The key principles to remember are Newton's laws of motion, which state that an object at rest will remain at rest and an object in motion will remain in motion unless acted upon by an external force. Another principle is the principle of moments, which states that the sum of moments about a point must be equal to zero for a system to be in equilibrium.

5. How can I check the accuracy of my solution for a statics problem?

You can check the accuracy of your solution by performing a statics check, which involves recalculating the forces and moments using different points or methods. Another way is to use the method of joints or method of sections to verify the results. Additionally, you can use common sense and logic to make sure your solution makes sense in the context of the problem.

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