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Nicholas Kang

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  1. According to BBC Knowledge Asia Edition, recession of galaxies are not known as Doppler Effect, they are known as Cosmological redshift. Why?

    Because Doppler Effect says nothing about motion of space-time continuum. It just tells you what happened to an object in motion THROUGH space-time. They speed away becasue the space-time is expanding. The galaxies hardly move at all. This is global space-time expansion, where gravitational effects become obvious. Locally, gravity effects are negligible. Therefore, the expansion of spacetime is not obvious, for example in Earth. Therefore, our distance remains constant if we are standing still. Recall that gravity is really a mathematical "trick" of space-time geometry.

  2. The velocity of an object with constant mass freefalling does not change because of gravity accelerating at a constant speed(9.8m/s).

     

    Acceleration means change in velocity.

    Velocity means Speed of an object together with its direction of movement-thus is is a vector quantity, unlike speed which is a scalar quantity without considering its direction.

     

    If I say a car travelling 60km/h. Its speed is 60km/h. The velocity is unable to be determined since the direction of motion is not given. But if I add a direction statement like 60km/h eastward. Then the velocity is 60km/h in the direction of east.

     

    Acceleration can therefore either be change in speed or change in direction.

    The velocity of an object with constant mass does change in free fall in Earth`s Gravitational Field since gravitational acceleration cause the object to accelerate, which means the velocity of the object would increase by 9.8m/s every second, for simple calculation, usually it is round off to 10m/s.

     

    If it drops at first second, the speed is 0m/s, after 1 second it is 10m/s, after 2 second it is 20m/s and so on. (Assuming gravitational constant is 19m/s2)

     

    It seems as though the height from which that object falls determines the amount of force with which it hits the book.

    The higher the height from which the pen falls the more force it exerts on the book (Someone can easily try and jump off a 1 meter high wall and land safely but jumping off a 3 meter high wall will surely result in some injury to that someone).

     

    This has something to do with momentum(but not in all aspects). Momentum = mass times velocity

     

    The height does indirectly affect the result. Since the higher the object from the ground, the longer the time available for the object to gain velocity. So, the higher the object is from the ground, the larger the magnitude of the final velocity when it touches ground. So, the larger the value for velocity. A large value of velocity times mass will give you a larger momentum, thus the greater the impact.

     

    To calculate the change in momentum, we can use Newton`s Second Law of Motion written in the "acceleration" version. Another version is the "mass" version.

     

    The acceleration version: F= (mv/mu)/t-----(1)

    The mass version: F=ma-----(2)

     

    We use the acceleration version in this context. Rearranging (1), we get Ft=mv-mu

    Ft=mv-mu. This product is known as impulsive force or change in momentum.

     

    Refer: http://fiziknota.blogspot.com/2009/05/impulse-and-impulsive-force.html

    (A Malaysian Form 4 16 years old Physics Syllabus Website)

     

     

  3. I agree with maths. But, to do maths, you need to think. Philosophy leads this field. Mind leads maths not maths lead mind. You do maths after deciding to work out the results. But thinking is the very first action. Shut up and calculate, the way I see it, are 2 different entities. The former deals with scientific noble values, which state the values that ought to be practised by a scientist-keep asking question(s), thus violating "shut up". The later deals with logistics and algorithm, stating laws and rules to be applied when doing calculation(s).

     

    Thus, why compare them? There are different matters to cope with. To apply scientific noble values, one just has to have an open heart and open mind to accept altitudes when doing science experiments. To calculate values and products for maths, one has to train himself/ herself to solve equations.

     

    Obviously, the problem is the phrase "shut up" and nothing to do with "calculate". Nothing wrong with "calculate". Mr. Andrew, Dr. Swansont, if the problem has to do with maths, why I don't want to start this topic in either mathematics or physics section? Because it is neither the philosophy of "calculate" nor the relationship between calculate and shut up that matters, but the real meaning of the "shut up" that counts.

  4. You won't have the knowledge at high school to really discuss this. At the school level you have an acceleration of test particle and so a force. You would need to go into some details about coordinate systems and a little differential geometry to begin to understand the pseudo-force nature of gravity. For a lot of phenomena you can forget all this and just use Newtonian gravity which fits into the standard picture of statics and mechanics as presented at school.

     

     

    So, why not teaching some basic knowledge at high school?

     

    Is this really the case? I am not sure.

     

     

    Try asking your students or simply conduct a survey then you will know the truth. Remember that the whole classical physics of high school is being overturned by modern physics of university, except some basic fundamental concepts that persist ever since it is being taught.

     

    Truthfully, it is not always fun but rather a lot of hard work.

     

     

    So, you should appreciate the process/progress of learning to enjoy it, instead of taking it as hard work.

  5.  

    The Planck distance is just a unit of measurement. It is based on universal constants rather than arbitrary human things like the length of the King's arm. As such, it doesn't change. So, yes, as the universe expands the number of parsecs, kilometres, furlongs and Planck units between distant object increases.

     

    So distance and displacement of an object isn`t constant anymore?

  6. why does mass affect space?

     

    I suppose this is the main question in this main topic.

     

    Minor corrections, remember that it is mass-energy affects space-time. Try to rethink this question by using energy instead of mass and time instead of space or even mass-energy affects space-time. Maybe the answer lies between the fact that the mass may transform into energy by Einstein`s famous equation. These 2 formulae should have some similarities too.

     

    E=mc2

     

    E=hv/E=hf

     

     

    Since virtual particles are a fundamental component of reality, isn't it appropriate to consider the virtual particles as space itself?

     

    I think the answer is no because virtual particles are located in space-time and you seemed to mix both GR and QM together since you stated both VM and space in one sentence. I would advise you to refer several Theory of Everything to check your answers, maybe string theory is a famous candidate, though not many(or maybe no) experiments are done regarding this theory. Combining GR,SR and QM has been the ultimate quest to unite Modern Physics.

  7. Only later will you need to worry about where it does not work so well.

     

    Why worry about it later? Since one day you will have to worry about it, why not worry about it now and solve your problems in the future, so that instead of worrying in the future, you can study other related subjects even deeper but not wasting time to worry about such matters in the future.

     

    And how do you explain the fact that most students have had their wrong(inaccurate) ideas anchored deep and firmly inside the brain, which means they face difficulities in university? Learning should be fun, shouldn`t it? But instead of learning happily, they have to struggle to change their mind, trying to cope with the correct(accurate) ideas, why doing things twice? Why making students continue to wander around the world full of inaccuracy and incomplete ideas?

    That is because the educational system is not only there to make you learn something but mainly to filtrate.

     

    In my opinion, you will learn how to filtrate when you learn something because this is one of the main reasons why you need to learn.

  8. Mr.ydoaPs Jr, although we haven't had any conversations before, I would still say congratulations. Teaching a child isn't as simple as it seems to be. Making your child obedient is even harder. But I know the almighty ydoaPs Jr is ready for it and I know you will succeed. Who knows one day your child will be Einstein. Congratulations!

  9. Ah, I thought you are Dr. swansont in physics. May I know which field are you specialized in? So, next time I can direct the correct question to the correct people. Sorry for asking things that aren`t your in your comfort zone. And thanks for answering the previous question.

  10. Ok, you basically solve one of my questions-why use conventional flow diagram instead of electron flow when the latter is proven correct. Yet, books like Understanding Physics by Robin Millar, University of York, New York, published in the 1990s use the electron diagram instead of the conventional`s. Can I ask you would the calculations of the circuit theory in conventional form affects the results of electron flow calculation in reality/real world calculations?

  11. You don`t trust Feynman? No, I don`t think so. You can refer to the link, it is a very short paragraph from a long article. I know the muon experiment. Because muon travels at the speed of light, so many of them experience time dilation, eventually they are able to survive at large amounts near the earth atmosphere. This experiment is mentioned in the book Einstein`s Relatively Simple by Ira Mark Egdall.

  12. Now, what should we teach first? Should we teach the correct but unfamiliar law with its strange and difficult conceptual ideas, for example the theory of relativity, four-dimensional space-time, and so on? Or should we first teach the simple “constant-mass” law, which is only approximate, but does not involve such difficult ideas? The first is more exciting, more wonderful, and more fun, but the second is easier to get at first, and is a first step to a real understanding of the first idea. This point arises again and again in teaching physics. At different times we shall have to resolve it in different ways, but at each stage it is worth learning what is now known, how accurate it is, how it fits into everything else, and how it may be changed when we learn more.

     

    This is a short paragraph from Feynman`s Lectures of Physics, Volume 1, Chapter 1 Atoms in Motions. Now, I know why, again sorry for posting useless topics. In fact, this topic won`t had existed if I had read the online ebook now. Thanks for support. I will try to keep myself as near as possible to the edge of Modern Physics and at the same time understand classical physics deeply and have a firm foundation before I proceed to Modern Physics, as imatfaal`s words conclude, you have to be able to walk before you run. Yes, I got it. So, thanks.


    Link: http://www.feynmanlectures.caltech.edu/I_01.html


    See paragraph 8.

  13. An article about the findings of swirls of wave patterns in The BICEP 2 in South Antarctica has shown that the physics of inflation is true. Alan Guth of MIT must be happy. The findings are published in a section in BBC Knowledge`s magazine Asia Edition. The book introduce quantum fluctuation and the fact that gravitational field is negative. I understand quantum fluctuation but why the field of gravity is negative. Here is a brief description from the book

     

    Imagine ions/atoms forming the sun spread over distance. Given the fact that gravity follows inverse square law, they would have zero gravitational force. When they eventually mix up and fall together and jostle between one another, releasing heat and light. The atoms start up with zero energy, so now they have negative energy. A simple calculation shows that the mass-energy of the atoms can simply offset the negative gravitational energy, so basically I have blots of star materials but out of nothing at all.

     

    Shouldn`t the gravity between particles increase as they get closer to each other? Why the magazine seemed to contradict this fact?

     

    Please shed light on this issue. Thanks.

     

    Serving the scientific community,

     

    Nicholas Kang

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