A couple questions regarding force and free body diagram

In summary: I think your questions are great and I am sure that many people would love to know the answers. However, I think that it would be better to post these questions in the appropriate forum. Force and Free Body Diagram Forum.Best,In summary, the shallow gradient in the stress and strain graph is normal according to my lab adviser, but it still stuck me. I'm not sure whether this is the right way to draw a free body diagram.
  • #1
Junkwisch
31
0
Hey guy, I would like to ask a few question about force and free body diagram.

First question, I conduct a compressive experiment a few day back, using compression machine to test the strength of different materials e.g., Aluminium, PVC and Ceramic. However there is one thing that I don't under stand in regards to this experiment. When the machine start working, the stress and strain graph somehow start up with a very shallow gradient instead of a straight linear gradient which one would expected for the elastic region (modulus of elasticity). This shallow gradient exists for all three experiments. I asked my lab adviser, which he hold me that this is normal. However, it still stuck me about where this shallow gradient come from... can anyone give me a clue for its existence.

The second question has something to do with a question I found on a textbook in regards to drawing a free body diagram. I'm a newbie at this and I'm not certain whether this is the right way to draw it. Can anyone give me a head up. (The question and my work out is in attach files)

Best Regards
Junkswischen
 

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  • #2
1) I assume that depending on how you attached the compressive element to the testing machine there was some initial slack to be taken up before the full compression load could be applied.

2) Your free body diagram for AB is not in equilibrium. The FBD for BC is looks right.
 
  • #3
You should put it in the homework section of the forum. You will get better responses.
 
  • #4
Ah, I see that make sense why the graph start out shallow.

For question 2, I thought the one that has a mistake in is segment 2. Is there any other force/moment involves in segment 1? I thought the only force acting on it will be Fcl and Fbc, could there be a bending moment caused by Fcl in segnment A?
 
  • #5
In order for segment 1 to be in equilibrium you have to sum all the forces in both directions to zero and to sum the moments to zero. So you are missing something.
 
  • #6
Seth.T said:
You should put it in the homework section of the forum. You will get better responses.

Moved. :smile:
 
  • Like
Likes 1 person
  • #7
Berkeman, Kudos to keeping this forum neat :)!
 

1. What is force?

Force is a physical quantity that can cause an object to accelerate or change its state of motion. It can also be defined as a push or pull on an object resulting from the interaction with another object.

2. How is force measured?

Force is typically measured in the unit of Newtons (N). One Newton is equal to the force required to accelerate a mass of one kilogram at a rate of one meter per second squared.

3. What is a free body diagram?

A free body diagram is a simplified illustration that shows all the forces acting on an object. It is used to analyze the forces acting on an object and determine its motion.

4. How do you draw a free body diagram?

To draw a free body diagram, you first identify the object and the forces acting on it. Then, draw the object as a dot or a box and label all the forces acting on it with arrows pointing in the direction of the force. Make sure to include the magnitude and units of each force.

5. What is the difference between net force and individual forces?

Net force is the overall force acting on an object, taking into account the direction and magnitude of all the individual forces. Individual forces, on the other hand, are specific forces acting on the object from different directions. Net force can be calculated by adding or subtracting the individual forces.

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