Free Body Diagrams

Physics homework for 11/12/14:

No. That's not what a free body diagram is; let's clear up what a FBD (free body diagram) is.

And let's also hear about what we did in la classe today in this little extra section. This section won't count towards the main part of the blog posts and will just help support and clarify certain aspects of what I am explaining. But since basically only my classmates and teacher will be reading my blogs, I don't need to really explain everything again, right? I would like to reiterate though, just to recap and what not.

Today in class we drew many free body diagrams based off of different scenarios and discussed FBDs. We also went into unbalanced and balanced forces more towards the end through a reading (pg 167 I think?). Also, we focused on certain aspects and learned some new things about the forces so that our diagrams were accurate. For example, we learned about scenarios where things are thrown and we focused on normal force in relation to acceleration and what not. Really, a lot could be reviewed from class but I won't touch it and let it be, especially since it is not really needed as much here. 

Now, what is an FBD/free body diagram? No, it is not a diagram of free bodies of people and what they look like. A free body diagram is a visual representation of all of the forces acting on a single body portraying each of the forces' magnitudes and directions in a given situation. Or simply put, it's a good way to show your situations involving the forces through pictures and it shows what the forces are like and what they are doing in that diagram based off of a specific situation. It is a good tool to help in better understanding and representing the forces and has many other purposes as well most likely. Not all forces are in FBDs, though in some many forces are shown. With FBDs you must properly follow along with the details of the scenario you are assigned and you must properly label and draw everything. Size your arrows correctly and from the center of mass. Label gravity first as a tip if gravity is appropriate according to your scenario. Also, draw one object; the object being focused on and mentioned. Sometimes various objects are involved, but pay attention to just what the description says and is talking about, then go from there.

So now do you understand what a FBD is smart cookies? :DD Not that you needed that explanation :33.

Person: Is it this? 

 That's... Better? (No, it's definitely not a FBD, sorry :-(((().

 

Here are the links I used: http://www.physicsclassroom.com/Class/newtlaws/U2L2c.cfm#1 and http://www.physicsclassroom.com/Class/newtlaws/u2l2c3.gif

The FBD above was drawn based off of this scenario from the website I got the picture from: A girl is suspended motionless from the ceiling by two ropes.

The object in the free body diagram is the girl that is mentioned in the scenario I pasted and the girl is represented by a box which most bodies are usually always represented by. While we have not really drawn and/or discussed diagrams with tension force as much it is very easy to understand and is good to be exposed to.

The object here is not moving on its own or at all; the description states the girl is suspended motionless. The girl is just hanging from a ceiling by two ropes and will not be in motion until something causes motion like a force or like energy (even air possibly). 

While the girl may not be moving, there are still forces acting on her just as upon us. And--*hears Ms.Reid's voice echoing throughout my head saying "what's the first force we always label?"*--s-sorry... And the first force we always label is the force of gravity. Gravity is probably in every single FBD UNLESS the details state otherwise (sometimes the scenarios may occur in a vacuum or in space so gravity won't be acting on an object there most likely but that's a different topic). Fg (gravity) is present here and is the force in the diagram with a magnitude equivalent to that of the opposing force in the diagram. Gravity usually always acts downwards on an object like it is here on the girl and it is what is keeping the girl not near the ceiling, but hanging from it (well, the ropes technically are suspending her, but the strength of our gravity keeps her from floating). Gravity is pushing her down, but not enough to make her fall to the ground luckily and notice that there is no F(N) (normal force)--why? And why is she not falling to the ground then?? Or why is she motionless?? Well, the girl is in the air, not on a surface of some sort where normal force would be in action perpendicularly so there is no normal force and while we know normal force keeps objects from accelerating downwards other forces can also help balance out other forces and can also help keep an object up (balanced forces in general are the reason behind some objects not accelerating and this diagram is most likely balanced). Tension force is that force in this diagram, and it is the only other force acting on the elegant swan dangling from the ceiling. Tension force here has a similar magnitude in comparison to the gravitational force, and is thus keeping the girl from falling entirely.  Tension force is acting upwards, opposing gravity in equivalent amounts and is really coming from the ropes.Yeah, expect a lot of suspension and roping when tension force is mentioned; that's usually where it comes from. And all though tension force seems smaller than the gravitational force it really is not and is just broken up into two pieces because there are two ropes. Besides, if the girl is motionless the forces around her MUST be balanced from what I know, I believe there are exceptions for certain scenarios but here it most likely needs to be balanced. My only constructive criticism toward the diagram would be how tension force still looks smaller than the gravitational force, but nonetheless is pretty good. 

Lovely diagram, eh? Poor girl :((.

And I should make it clear that she is not up close to the ceiling, if she's hanging from the ceiling then gravity must be stronger than the tension causing her to hang, but there is still enough tension force to keep her partially up in the air. It makes sense since the net force would cause the girl to be either closer up to the ceiling or farther down because with net force usually an object is not at rest. (Wrote this earlier, DO NOT make this mistake. I believe I was wrong here).

EDIT: The opposing forces are actually most likely balanced here because if they were not the girl would be accelerating downwards which she is not doing. Maybe gravity is stronger than the tension force somehow and that is why she is hanging from the ceiling, but at the end of the day she was motionless and that was because of the balance between the forces. There was no net force. If she was motionless, she had to have been balanced technically. I cannot edit the paragraph above at this moment, but keep in mind that what I wrote above is not 100% accurate. Sorry. The only reason why she is dangling from the ceiling is because the ropes are keeping her at that position now that I realize it. 

And a little conclusion: Forces for me has been the hardest strangely, not unbelievably hard, but moderately tough. But, I will probably ask for help soon and look wherever I can to clarify things.



(Technically honors physics but close enough @w@). (Irrelevant but very true and explains everything about me *cries*).

Also, I accidentally searched "Fapp" while on Google Images to look for applied force..
Needless to say I sincerely regret that and need to drown myself in bunnies for the next three hours. Good night ;w; <3 . (Kidding, but seriously guys don't EVER search "fapp" good gravy on goose ghosts it will be fghdfgf- DD:)

 YES, NOW STARE INTO ITS SOUL OR FOREVER HOLD YOUR PEACE MWUAHAHHAHAHA

sorry, i love bunnies a lot bye bye ;w; <3 

(Note: Anything in italics or bold probably are not major details, though they do help a bit. The main meat is the normal typed words).