# Internal Forces in Statics

1. Nov 7, 2004

### Double A

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
Question 1 (http://herograw.com/7-20.JPG)

My free body diagram looks like: Free Body Diagram 7-20 (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 $$\Sigma F_x = 0, \Sigma F_y = 0, \Sigma M_A = 0$$. 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: Question 2 (http://herograw.com/7-32.JPG)

My free body diagram is:Free Body Diagram 7-32 (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 ($$\Sigma F_x = 0, \Sigma F_y = 0, \Sigma M_A = 0$$). 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:Question 3 (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.

Last edited: Nov 7, 2004
2. Nov 8, 2004

### Double A

No one has any idea! I guess these questions are very difficult. Is there anyone who can help me in the least bit?

3. Nov 8, 2004

### Double A

:surprised I guess there is no hope after all... :grumpy: :yuck: