# Tagged Questions

DO NOT USE THIS TAG just because the question deals with a law of physics!

385 views

### Justification of Physical Laws [on hold]

I'm a maths student, and I've studied quite a lot of mathematical physics. All my courses have a similar style - we state the laws of the system, and then deduce the physical consequences as theorems. ...
314 views

### About time and time dilation [closed]

This question is related to this answer of John Rennie. He says: The length of the red line is the same in both figure 1 and figure 2 I guess his meaning of red line is the space-time distance ...
155 views

### Do we not need a Zeroth Law of motion similar to the Zeroth Law of Thermodynamics? [closed]

Is the Zeroth Law of Thermodynamics necessary? If so, then do we need a similar law for motion?
108 views

### Can we have a physics by using other mathematics except calculus? [closed]

We (I) always have been said that we don't need to real values, we just need to differences. For example, $\mathrm du=C_v\mathrm dT$ and $\Delta u=\int_{T_1}^{T_2}C_v\mathrm dT$. So, I have some ...
69 views

### What's the difference between hypothesis, theory and law? [closed]

What's the difference between hypothesis, theory and law? I think I'm confused now because I exactly learned the misconception one as explained below in high school. According to this university's ...
71 views

### Observation and deduction about a stick

Given a horizontal stick AB and a string, of course a stick that is hang on the string in its center of mass is in equilibrium. This is a fact that we take as rule because we can observe it, right? I ...
42 views

### Growth and Decay, Law or not?

The differential equation for decay that applies to radioactive decay is: $$dN/dt=-kN$$ for a positive constant k and number of particles N. My question is: is this, strictly speaking, a "Law"? I ...
45 views

### Difference between integral and differential physical laws [duplicate]

Why is integral and differential physical laws both used? I read that integral is global and differential is local. Could you tell me something about it?
74 views

### How are laws proven in general?

This may be a bad question, but what are the ways that laws are proven? I would expect that some ways would include by proving them mathematically or through experimentation. My biggest question about ...
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### Classification of experimentally-determined physics laws? [duplicate]

Has anyone classified (or attempted to classify) all the experimentally-determined laws of physics, such as with a simple diagram or even in a full-length book?
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### While deriving Coulomb's Law from Gauss' Law, the power of 'r' comes out to be exactly 2 while experiment shows that it differs about 10^(-16). Why?

While deriving Coulomb's Law from Gauss' Law, the power of 'r' comes out to be exactly 2 while experiment shows that it differs about 10^(-16). Why is it so? I'm referring to the book 'Physics by ...
90 views

### Injectivity of Physical Functions

Consider all functions in nature (except path functions like work) like internal energy, modulus of elasticity, electrical resistance of a material, etc. 1) Is there any function (as described above) ...
23 views

### Calculating the change in aceleration the earth feels when you push an object

I am learning newton's third law, and i got to this conclusion, i wanted to know if it's correct (within the boundaries of Newtonian mechanics) Say I'm pushing a cupboard with my body, and I apply a ...
21 views

### How are proportional relations derived in physics?

I would like to ask a simple question :How are proportional relationships in physics found? To be more specific, let's consider a simple law, Ohm's law, which states $\Delta V\propto I$. Now, it ...
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### Justification of the State Postulate

I have just started thermodynamics (not with statistical approach but with macroscopic approach), in which the state postulate reads Only two independent intensive properties of a simple ...
57 views

### Physical and non-physical solutions to Einstein's field equations

Einstein predicted gravitational waves in 1916 as a solution to his field equations. Apart from doing experiments, is it possible to tell which solutions exist in the real world and which don't? Are ...
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### Symmetry and present value problems

Suppose we don't know any physical law of nature and we're studying, a system. Let's say a uniformly spherically charged distribution. Now this distribution has the property, that if you rotate this ...
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### Why is there empirical evidence in physics more than an analytic evidence? [closed]

In case of mathematics, you can make your own rules and play with them. For example, Euclied made his own rule of Eucledian geometry, and Reiman (or other Non-Eucledian geometers) made their own rule ...
1k views

### What came first, the Universe or the Physical laws that govern the Universe? [closed]

This sounds like the Egg and the Hen question but I am curious about this. If universe came first and created physical laws for itself, then what created the law or the principle as a consequence of ...
74 views

### Friction in driving car

We know friction helps in driving car, does this mean car can move faster on rough surfaces ? Since coefficient of friction is more on rough surfaces
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### Newton's Third Law? [duplicate]

I've recently met with this new law and the way my teacher worded is so off for me. Shouldn't the equal and opposite reaction cancel out the action because they are equal? Apparently not? Why?
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### Balanced and Unbalanced Forces Help

I am a newbie pondering in Physics concepts. I just had a question about Newtonian physics. The reason why "everyday" objects come to a rest is because there are unbalanced forces working against ...
317 views

### How is an object kept on a table is at rest?

When there are two bodies A and B lying in contact we can apply Newton's third law which says that the action and the reaction act on different bodies and not on the same body. That is why two forces ...
157 views

### Can pure mathematics alone give proofs in science [closed]

I reasoned in my last post that because of science's nature of induction and falsifiability, it is impossible to give a theorem in science, unlike in mathematics. It is because even when a scientific ...
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### Which laws of physics does this problem break?

One of the problems from the Google Code Jam programming competition, round 2 2015, goes like this: A kiddie pool is a big container in which you can put water, so that small children can play ...
84 views

### Bending along an axis for strength?

I read about this law / property a couple of months back, but I've forgotten what it's name was and I can't seem to find it by Googling. I was hoping someone could give me the name for this property. ...
45 views

### Laws of physics for a point in cyclical 2D motion

A follow up question to the question in What does the statement "the laws of physics are invariant" mean? and Formal definition of an observer? Which laws of physics are they talking about ...
11k views

### Why do most formulas in physics have integer and rational exponents?

I mean, why is $F=ma$? Why not $m^{0.123}$, $a^{1.43}$ or some random non-integers or irrational? I hope you understand that my question isn't limited just to force, energy, velocity, etc.; it also ...
83 views

### How to conclude that some correlation does imply causation

I'm trying to prove that all physical THEORIES are just experiments and tests that conduce to assumptions about correlations between causes and results. BUT how physicists conclude that a relationship ...
897 views

### How is mass reduced in a normal chemical reaction which releases energy like heat, sound or light?

I was reading this link. Just above the paragraph titled "OTHER CONSERVATION LAWS", it says that "This conversion of mass to energy happens well below the speed of light, in a very small way, when a ...
164 views

### Proving (instead of discovering) the laws of quantum mechanics

A single toss of a fair coin cannot be predicted. But if we observe a large number of tosses, we can prove mathematically the law that roughly half of them will show up heads. The movements of ...
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### Locus of a moving mass point

Two very small mass particles $m_1$, $m_2$ are connected by a $2l$ long, infinitely soft and inelastic thread without mass. The initial condition of the system before being freely released is as in ...
456 views

### Why Light and Observers have different laws of physics [closed]

Special relativity states: The speed of light in a vacuum is always $c$, regardless of the velocity of the observer. The laws of physics are the same for all observers in uniform motion. These two ...
66 views

### Question on the provability of the physics laws of the Newtonian Mechanic

Why the physical laws like Newton's law of motion can't be proved? Or more specifically: why our Universe follows laws?
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### Different equivalent representations for same physics

I want to expand my understanding of physics and just watched a Feynman lecture where he said "every theoretical physicist who is any good knows six or seven different theoretical representations for ...
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### How do you interpret the product of two components?

I hope this isn't borderline philosophy. It is really difficult for me to articulate the question and so Google was of no use to me. The question spawned when I was learning laws of conservation of ...
1k views

### What is fundamentally physically impossible?

Mathematical logic defines quite clearly what is true or false in math, and also that some theorems are impossible to prove. This resulted in some clear definitions of axioms set like Peano, ZF or ZFC,...
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### If the universe could emerge from nothing, what about physical laws? [closed]

I've watched Lawrence Krauss's lecture and read his book. I think I got what he was saying, and I don't have any problems with that; however, what I can't get is how the laws of physics that makes ...
371 views

### How to know if something is a primitive concept, a law, a definition or a theorem

Some basic Physics books are often misguiding in the sense that they don't make clear whether something is a primitive concept, a law, a definition or a theorem. This is often a little confusing. I've ...
196 views

### Inverting the laws of physics [closed]

Are there any good theories on inverting the law of physics? To make physics work the opposite way of what it does. Please ask question if this is unclear! I'll answer as well as I can. Ok, I'll ...
181 views

### Do physics laws really apply to anything? [closed]

My professor said that a law was stated and announced as a law because it happens in our everyday life. He gave us an example of Newton's 3 laws. He said that walking possess 3 laws of Newton's. Is ...
356 views

### Evolution principle of the physical laws

I wanted to know if there is a physical theory that considers that the laws of physics undergo an evolutionary process. That see the law of physics or the absence of them, as something dynamic, and ...
270 views

### Can we write down a dynamical law of physics which is totally non-deterministic?

In classical mechanics, $F=ma$ tells us how to evolve a system at time $t=t_0$ to $t=t_0+dt$. In quantum mechanics, the Schrodinger equation gives us a similar recipe. These equations are, in a ...
835 views

### Aren't all physical relations non-linear?

It is well-known that Hooke's Law is only approximately true and thus that linear relation is merely an idealization not strictly corresponding to the reality. Wouldn't it be necessary/appropriate ...
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### How can we claim something violates some physical law, when so many physical laws have been postulated?

For example, Einstein postulated that the speed of light, c, is constant in all inertial frames of reference. Bohr postulated that electrons go around the atom in ...
141 views

### Has there been any serious work in how the world would look if basic physical laws were changed?

Has there been any serious work in investigating how the world would look if certain basic physical laws were changed? Like if gravity or electromagnetism laws were changed to have different ...
360 views

### Is energy extensivity necessary in thermodynamics?

Given a partition of a system into two smaller systems, the energy $U$ is devided into $U_1$ and $U_2$, with $$U=\mathcal{P}(U_1,U_2):=U_1+U_2,$$ so that $U_2$ is given by $U-U_1$. Here the ...
873 views

### Why didn't Newton just propose the 2nd Law and leave it at that?

Why didn't Newton just propose the 2nd Law ($F=\dot{p}$) and leave it at that? The 2nd Law implicitly contains the first, doesn't it? If so, it seems he wasn't following his own Rule #1 of Book 3 of ...