How do I solve internal force problems in statics?

In summary, the student is having trouble with three questions on their statics assignment. The first question is about finding the largest internal force in a system, the second question is about finding the reaction forces, and the last question is about finding the internal forces acting at a section point.
  • #1
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Please Help! Internal Forces in Statics

I have been attempting to answer the problems on my Statics assignment for about a week now but I have not been so success full. I have only be able to answer on of the problems the other three below I get stuck on. Can someone please help me get past the areas where I get stuck?

The first question that I'm having trouble with can be found by following the link below
http://herograw.com/7-20.JPG

My free body diagram looks like: http://herograw.com/fbd7-20.JPG

I'm not sure if that is the right the free body diagram and I am unsure as to how I can find the that largest virtical force. I'm wondering if I should leave the cable in the free body diagram that way its interaction is internal to the system and only have three unknown to find using [tex]\Sigma F_x = 0, \Sigma F_y = 0, \Sigma M_A = 0 [/tex]. Then I could go onto finding the internal normal force, shear force, and moment at the section C after I make free body diagrams for the section.

The second question is: http://herograw.com/7-32.JPG

My free body diagram is:http://herograw.com/fbd7-32.jpg

In this question I am comming up with four unknowns (Ax, Ay, Cx, and Cy), but I only have 3 equations to use ([tex]\Sigma F_x = 0, \Sigma F_y = 0, \Sigma M_A = 0 [/tex]). I don't think member AB is a two force body because there is an applied load acting on it. I'm not sure as to what I should do finish this problem. I need to know what the reaction forces are before I can find the internal forces acting at the section point D.

Lastly:http://herograw.com/7-40.JPG

This question confuses me. Could someone please clarify some as to what I need to do solve this question. I'm not sure how to make my free body diagram. I need a starting point and I can't seem to find one on my own.

Someone please help. I have to get this done before Tuesday. I thank all who can help in advanced.
 
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  • #2
No one has any idea! I guess these questions are very difficult. Is there anyone who can help me in the least bit?
 
  • #3
:bugeye: I guess there is no hope after all... :cry: :mad: :grumpy: :yuck: :frown:
 

1. What are internal forces in statics?

Internal forces in statics refer to the forces that act within a structure or object, rather than those that are applied externally. These forces can include tension, compression, shear, and bending forces.

2. How do internal forces affect the stability of a structure?

Internal forces play a crucial role in determining the stability of a structure. They must be balanced and distributed evenly in order to prevent the structure from collapsing or deforming. If internal forces are unbalanced, the structure may experience stresses that can lead to failure.

3. What is the difference between internal and external forces?

The main difference between internal and external forces is their point of origin. External forces are applied to a structure from outside sources, such as gravity or wind. Internal forces, on the other hand, originate within the structure itself and act on its internal components.

4. How do internal forces relate to Newton's laws of motion?

Internal forces follow Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. This means that internal forces within a structure must be balanced in order for it to remain in equilibrium.

5. What are some examples of internal forces in everyday life?

Some common examples of internal forces in everyday life include the tension in a rope, the compression in a column, and the bending forces in a bridge. These forces can also be observed in the human body, such as the compression in bones and the tension in muscles.

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