Tuesday, December 7, 2010

Don't break these laws, Newton is the new sheriff in town

Newton's First, Second, and Third Laws of Motion

This is my tagxedo that I created with all of the important words the were a part of our unit.

In the latter part of our first trimester, and beginning the second trimester, we have learned about Newton's first, second, and third laws of motion. Basically, we learned when an object is in translation equilibrium, how to find vector sums, that when one object exerts force on another, the second object exerts an equal force in the opposite direction, and finally, that if there is any net force on an object, then it will have an acceleration.

In the first law of motion, I started off with it with a pretty solid understanding of it. However, as one can imagine, as we got into harder problems involving more complicated processes it became more difficult. We began to look at problems with multiple angles in which I would have to make sure to include each cos and sin to assure that I don't miss a step. It is all a lot of breaking down each individual force, and making a logical equation that is based on the forces acting on the x and y axises. This was definitely the most difficult part because I had to incorporate the different angles and a lot of the time it just all got jumbled up. I finally found the key and that was to, as it was in my previous post on vectors and projectile motion, to once again break everything down. This is the only way I could solve this problems. However it took me longer, but in the long run, I eventually got faster and was able to just take things step-by-step-by-step.

In the second law of motion, the law that we have just recently begun in this new trimester, I so far have a complete and total understanding of it. This is essentially how forces affect the amount of acceleration an object has, leading to the amount of velocity it gains or loses. My sole weakness of this law is mastering the problems in which I have to slow down and replace things such as "Fg" with "mg" and so on and so forth. In general though, this is quite an easy unit/law for me. I simply have to, in my head, think of what parts of the equation I have and don't have, leading to which parts of it I need to find or replace with information I already have.

Finally, in Newton's third law of motion, the law states that any two objects in which object "A" is exerting force on object "B", object "B" exerts the same force on object "A" in the opposite direction. There is the action force and the equal but opposite force is the reaction force. This law didn't require a whole lot of problem solving, for it mainly just helped in my understanding of laws one and two. The third law is of paramount importance in the understanding of the other two, because without it, one wouldn't realize that forces Fg and Fn cancel each other out. This is because of N3L because these two forces acting on the same object constitute an action-reaction pair of forces.

Now, in putting all of these laws to problem, we learned about apparent weight, the forces in pulley systems, and friction. In apparent weight it took a hard thought process of making sure we were using the right forces when adding and subtracting based on if an elevator is moving up or down, etc. In our section on pulley systems, they were quite easy for me. It's like solving two problems, leading to two free-body-diagrams, which led to essentially solving for the same exact thing, just taking both objects into account. Finally, in our study of friction, we learned a lot about "Mu" It was really interesting to learn about why friction actually exists. I felt like applying the concept of N3L to this section made it easier because in N3L, there is an action and reaction pair, leading to equilibrium in the y-axis (in most cases). Similarly, friction and tension or applied force lead to somewhat of the same thing.

In conclusion, the study of the three laws of motion in our physic's class was a fun unit, for it revolves around what most people consider the "basis" of what they know as physics (one's knowledge of the physics in moving objects). For solving problems that I ran into, I had to evaluate the problem for which law it was based on, and how I could apply that law. Even when a problem seemed hard, I had to go back to the basics and remember equations that resulted in Fg, Ff, etc. These equations are what allowed me to substitute for what I needed, or at least substitute for something that would allow me to find another number.

Good bye for now, physics world.

5 comments:

  1. It is a very good blog posting. You cover everything she says to cover except that I would give a slight definition, in your own words of course, on law one. In the other two you sum them up well and give examples of what you did in those sections.

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  2. Overall you did a good job with your reflection.
    There are a few items that need to be updated.
    You claim that N3L is responsible for the normal and gravitational force to be canceled out. Do these forces constitute an action-reaction pair? Are they acting on different objects? If so, how come they cancel out? Please investigate this and correct your statement.
    Your explanation of content is a little superficial as there is no mention of the cases we studied: apparent weight, pulley systems and friction.
    Also, when you talk about problem-solving skills you have to provide a very specific example of your weaknesses and strengths. Talking about equations and problem-solving steps is very general and can be applied to any topic in Physics. Please be specific.
    Looking forward to reading your final posting.

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  3. Thank you both, sorry for the late response, I got caught up with a lot of stuff Sunday and completely forgot. Mrs. Gende, the only reason I didn't include those topics was because I thought we were just reflecting on the sole ideas of Newton's laws, and I see what you mean now by how my previous problem-solving explanation could be applied anywhere. And I did revise my N3L paragraph, thank you, meant to include more detail to begin with.
    Tori- thank you, I added a little more definition to N1L to make it a little more clear, hope it works out better!
    Thanks

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  5. Great job in the majority of items but just to clarify:
    N3L refers to forces acting on DIFFERENT objects. These forces NEVER cancel out. Gravitational and normal forces act on SAME object and therefore they may cancel out but they are not an action-reaction pair.
    Also, N3L is never used in solving problems like the ones we did in class as we usually focus on ALL the forces acting on a system.

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