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What makes mechanics mechanics?

  1. Aug 20, 2015 #1
    So, i have had this dilemma for a while now. I am trying to reform my curriculum (high school physics). In doing so, one question keeps popping up. What makes mechanics mechanics? A simple google search yields definitions as the branch of physics dealing with motion, or dealing with objects subject to forces, or the behavior of objects under any effects. Clearly these are too broad. Motion is perhaps the one unifying phenomenon studied in physics. Is mechanics synonymous with physics?
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  3. Aug 20, 2015 #2
    In the classical sense mechanics is the study of motion and how it is caused/altered. Contrast this with kinematics which simply seeks to describe motion.

    I feel like one could argue that, but I think that 'physics' is more inclusive than 'mechanics.' For example, kinematics is part of physics.
  4. Aug 20, 2015 #3


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    How so?
  5. Aug 20, 2015 #4


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    Mechanics is about fixing cars, surely?

  6. Aug 20, 2015 #5
    I do love that cover. Almost as good as his Introduction to Error Analysis cover:

  7. Aug 20, 2015 #6
    How do you define mechanics, then? Electrons moving across a wire is motion. Is this mechanics? Do we study magnetism and related magnetic forces in mechanics? Do we study the motion of a light wave in mechanics?
  8. Aug 20, 2015 #7
    I suppose that in conversation I would refer to the motion of charges as electrodynamics. Perhaps the distinction has to do with bulk motion vs. individual motion. For example, the kinetic theory of gasses certainly has to do with the mechanics of particles. We could call the consequences of this statistical mechanics or we could not look at the state variables instead and call it thermodynamics. If I were to consider a problem that involved energy transfer between two gasses I might consider that a problem in thermodynamics even though it really boils down to a problem of 'mechanics.' Further, if we're talking about light where the ray approximation is reasonable I would call it 'geometrical optics' because the individual motions aren't necessary to follow; if the individual motions were important to follow I suppose it would be a problem classified as quantum mechanics.

    If I may ask, why the naming of this important for revamping your curriculum?
  9. Aug 20, 2015 #8
    After my first year of teaching, i have come to hate my curriculum. First we teach mechanics, then towards the end of the year, we move to electrostatics and circuits. A lot of what we teach goes against the very research into this field. We teach students to plug and chug, and our assessments and labs reflect this.

    Mechanics has been my target for a couple of reasons. When i shift over to electrostatics, we make a huge jump, that should not be made. We are still discussing energy, forces, and motion, but it feels completely different. We also jump around a lot in our examples of mechanics. Over the course of three-quarters, we will teach about a ball falling down, a car crashing, a planet moving around the sun. We will show a way to explain the ball falling, then put it aside, then revisit it again in energy.

    Research shows two critical issues in learning physics today. Students struggle with explaining physics concepts and they fail to see a connection with what they study and the real world. I put a lot of the blame on the study of mechanics.

    As i see it, mechanics is really the study of common motifs in physics. In mechanics, we will study kinematics, forces, waves, momentum and energy. We will mask these themes with examples that sound realworldy, but is far from it. Cars don't crash in nice isolated systems, but we say they do. The dropping of a ball isn't that important, but it's a nice example for gravity (something that is important). I want to separate these motifs from bulky or macroscopic motion.
  10. Aug 20, 2015 #9
    Mechanics being the study of the motion of bodies or systems of bodies under the influence of forces ( in which the Heisenberg uncertainty principle can be neglected of course) permeates most aspects of physics to some extent. Its main intent I think is to specifically develop the formalism to deal with motion of objects under forces in general. It forms a basis for beginning the study of other branches of physics in which particular forces are identified.. It can be applied to E/M for example but this is just one aspect of E/M. Its concepts have been extended to Quantum Mechanics and field theory in a more abstract way.
  11. Aug 20, 2015 #10
    Well kudos to you for undertaking what might be an enormous task. I did a major overhaul myself this summer (for different reasons).

    I wouldn't blame mechanics for this - just the way it was being taught. I think it is quite possible to explain concepts and applications of mechanics in a coherent and meaningful way even at the high school level.

    Part of learning physics is learning when it is appropriate to make idealizations. I think that can be effectively communicated to the students.

    Perhaps the dropping of a ball doesn't seem that important now, but what if you put it in the context of the 16th or 17th century? How a ball drops not only leads one to discuss free fall (obviously), projectiles, conservation laws, universal gravitation, mass vs. weight, and probably more that didn't make the short list. One thing I find missing from almost every physics text is the historical context which is equally as important as the application.
  12. Aug 20, 2015 #11
    Doesn't research indicate that the problem is with the classical lecture/homework format where the student sits passively listening the a presentation and then asked to apply what was suppose to have been learned from the lecture?

    So not the subject itself but how it is presented. Physics is the study of interactions and the result of them. Mechanics deals with this directly and explicitly.

    Don't current trends in teaching involve the active participation in the learning process, extensive sessions in which the student can explore physical principles and actually see or experience their effects?

    Additionally physics is different from what the student normally experiences. It is not a collection of facts to be memorized and regurgitated like so many of their other courses. It involves thing that the have seen but not in a way that they have usually thought about them.

    I've come to appreciate teaching the arts to disinterested students through my own adolescent indifference when I took those courses. When I read poetry I read words. When I look at a painting I just saw a picture. I know now that must have been frustrating to the teacher to see students missing the point of the class.

    So too with physics the method not the subject must change. One must admit that he/she may also not have the skill to present the material in the most interesting or engaging way, but admitting it may provide impetus for improvement.
  13. Aug 20, 2015 #12
    This is my issue, though. There is no good definition of mechanics. Let's use this definition.

    I can create a curriculum, in which we study for the majority of the year e/m. We can study forces, kinematics, energy, and so on. It conforms to this definition, as we are studying bodies under the influence of forces (it's hard to avoid this!). So, in effect i am teaching a course in mechanics.

    I find that it is important, but when taught this way, it loses its connection to the real world. Feynman admitted that physics courses are designed for the student to major in physics. Students generally leave physics thinking that it has less to do with the real world, than when they first entered. I feel the need to stop telling the students they "will understand and appreciate it later". For the majority of physics students, there is no later.

    I feel as if this is one piece of the puzzle. Just doing physics doesn't increase understanding.
  14. Aug 20, 2015 #13
    If in doubt, try the OED

    The branch of applied mathematics dealing with motion and forces producing motion.

    Seems good enough to me. There are a certain breed of scientists that prefer obfuscation to clarity.
  15. Aug 20, 2015 #14
    Actually I think studies say differently. The student is more focused and involved if the sessions are done right.

    Well It might work, coulomb force vis-a-vis gravity but the Lorentz force may introduce a complication being a vector product. and you would also loose the constant acceleration scenario and related projectile situations.
  16. Aug 20, 2015 #15
    I guess I'm confused about what you mean by 'real world' then. I think providing context (historical or otherwise) deepens the connection to the real world!

    Another thing I intend to do this year in my introductory physics class is to place an emphasis on valuing physics not simply for its application but as a 'work of art' (mechanics as poetry, if you will - to borrow from Hamilton). I think it is unfortunate that almost all the emphasis gets placed on applications because there is a valuable cultural aspect to physics as well. To paraphrase a quote on the internet (attributed to Feynman, but probably erroneously): "Physics is like sex. Sure, it has practical application, but that isn't why we do it."
  17. Aug 20, 2015 #16
  18. Aug 20, 2015 #17
    High schools get around teaching torque as a cross product. And you can use an electron moving between charged plates to show some kinematics. Not saying this is how you should teach mechanics. Just saying that they become indistinguishable when you poorly define (or fail to define at all) mechanics.
  19. Aug 20, 2015 #18
    So, i brought up the topic to my colleagues. One of them responded something on the lines of that teaching energy is important because it makes you a more informed citizen on our own energy issues. I fail to see how teaching that K = 1/2mv2 will make you an informed citizen on whether or not utilizing nuclear energy is good for our country.

    I do like the idea of using historical context. Can you please elaborate on this? I give a small historical context when i discuss gravitation, but nothing much.

    While i agree with that sentiment. I feel like we forget the applicative aspects of physics in class. I rarely ask the students to build anything. And when i do, i do not ask them to connect it with the physics they learnt in class (something i intend to change this year).
  20. Aug 20, 2015 #19


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    We'll, you gotta start somewhere. Too many people today can't tell the difference between a kilowatt and a can of beans.

    As far as most people are concerned, electricity is something that just comes out of a wall socket somewhere, but who otherwise have no clue about its generation, distribution, etc. Are wind farms a viable substitute for a large central power station? You can't begin to answer that question until your audience understands how many wind generators it takes to equal the output of an average-sized power plant.

    In the HW help forums here at PF, I come across many students who don't seem to grasp the concept of torque and moments at all, and who are quite perplexed by things like tension. It's all too easy, IMO, to teach physics without going to the trouble to give students practical demonstrations now and then.

    We have a chuckle at the book cover above showing a picture of someone working on an old car under the title "Classical Mechanics", but I can't help but think that today's student spends more time being entertained by playing with his phone or tablet than actually manipulating some device to see how it works.

    That's what intrigued Feynman so much about physics when he was young. He wanted to know why a clock or something stopped working, and his father had the presence of mind, instead of going into a lecture about time-keeping and such, to challenge his son to take apart the clock and see for himself why it didn't work anymore. It was striving to answer the question "Why?" that made Feynman the kind of physicist and scientist that he was.

    Today, no one sees what's going on behind the curtain with many common devices now, so any opportunity to explain or demonstrate why or how something works should not be passed up.
    Last edited: Aug 20, 2015
  21. Aug 20, 2015 #20
    Not a teacher but a student. A majority of my teachers would digress the lecture, and tell us what they are used for or how it was created. Ie. For my Linear Algebra Class, when we learned Cauchy Inequality, our teacher digressed and told us who Cauchy was and how he and others put mathematics on a rigorous footing. He even made a joke which was amusing. Remember the Epsilon/Delta in Calculus 1 you guys hate? Blame Cauchy!

    In my mechanics course. Our teacher would also tell us how these ideas are used in the real world. Sometimes, I would not understand her. However, as I read and learn more I have aha moments and remember the class conversations.

    I noticed that professors who have experience in industry are better lectures because they can make the class come alive. Professors who went straight into teaching, in my opinion, seemed like a box of random facts with no unification of ideas in sight.
  22. Aug 20, 2015 #21
    Unless they do something that is not presented in the typical introductory physics text then I would probably disagree with them. At my school we offer a class called 'Energy and the Environment' which is more oriented around energy policy and aims to address the 'informed citizen' idea. I have not taught the course (in the future I hope to co-teach it with the chemistry teacher); in my physics classes we don't delve deeply enough (or into the appropriate topics) to make me think that what I've taught students makes them informed about energy 'issues.' What I used to cover is pretty close to what you'd find in any college level introductory mechanics text with some thermo mixed in.

    Last year I started incorporating more history into my introductory physics class (on almost every topic) and I liked how the students responded. This coming year will be a big experiment for me as I've changed the curriculum to actually trace the historical development of physics. So take from this what you will - it isn't tried and true yet.

    I'm not sure how much detail you are interested in, but I think I have a somewhat novel approach to a first year physics course. While most courses start with Newton (or, more likely, Galileo), I plan on starting with the Egyptians and Babylonians and ending with Newton. In some ways I feel like I have designed a prequel to an introductory physics course except that the depth on some topics exceeds what is typically taught. Along the way students will read excerpts of relevant (translations of) primary sources including works by Plato, Aristotle, Euclid, Archimedes, Augustine, Buridan, Oresme, Copernicus, Kepler, Galileo, Pascal, Bacon, Descartes, Fermat, Huygens, and Newton.

    I've never seen physics done this way. I'm pretty excited about it. I think I'll end up hooking more students interests because they'll get history, math, science, literature, philosophy, and even art all in one class.

    If students opt to take a second year we'll essentially be able to pick up where we left off. I'll plan on delving into the development of calculus and the completion of classical mechanics - hopefully even getting into Lagrange's Analytic Mechanics (so they can really see mechanics as poetry!). I've yet to work out the details of the second year though.

    If it helps, these are some things I have done in the past/continue to do as long term projects include
    1) Simulation of Global Armed Aggression: As part of the unit on projectiles students build large scale tennis ball launchers from surgical tubing/lumber/pipe which can launch projectiles about 3/4 the length of the soccer field if built well. The simulation involves a rather intricate set up that is meant to model how natural resources, economics, and politics affect global conflict. The connection to physics has more to do with technology - I have allocated resources in various ways throughout the time I have done this project to give certain groups/countries advantages/disadvantages over the others.

    2) Hobo Stoves: students design and build stoves from tin cans and measure their energy efficiency. Students then attempt a modification to the stove which they believe will improve the efficiency. This is essentially a calorimetry project but it is really fun.

    3) Engineering competitions hosted by local colleges/universities: I have done an assortment. Unfortunately some of them no longer exist due to funding cutbacks.

    4) Rockets: usually with my advanced class because there are fewer kids (less $). Plus I teach them how to incorporate air drag into their model. What I need is space for a small wind tunnel to make this project complete.

    5) Battle 'RC' cars: I haven't done this for years (It was my mentor's project and I don't have the materials since I changed jobs). Have students modify RC cars so they are hard wired to a control box that they make which gets plugged into a wall outlet. Then they play 'king of the hill' with their cars which can be equipped with weaponry to claim the hill.
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