# What are the basic Laws of Physics

1. Sep 4, 2011

### mat1101

I am 14 and know Newton's laws, but are there more basic laws of physics either then Newton's? If you could tell me or give me a link that would be great!

2. Sep 4, 2011

### boyongo

You can go and read about The laws of universal gravitation, bernoulli's principle, laws of thermodynamic, Coulomb's law, Ohms law. You can start.

3. Sep 4, 2011

### diazona

Well, it depends... if you mean "basic" in the sense of "easier to learn" then no, Newton's laws are the simplest. But if you mean "basic" in the sense of "more fundamental" i.e. something from which Newton's laws can be derived... well, sort of. The thing is, the math required to understand them is a lot more sophisticated than what goes into Newton's laws. It's usually the content of a first- or second-year college course.

Let me attempt a quick conceptual description, though. Most people who know about such things would say that the most fundamental law of physics (as we understand it now) is the principle of least action. The idea is that any problem in physics can be understood in some sense as a transition from an initial state to a final state - for instance, a ball starts at the top of a hill (initial state) and rolls down to the bottom of the hill (final state). There are many different ways that the ball could get from the top of the hill to the bottom, and to each of these ways you can associate a number, called the action. Most of the ways are unphysical, i.e. they would never actually happen - for example, the ball jumps off the top of the hill, hovers 3 feet above the ground all the way down, and then drops at the bottom; or it digs through the hill and comes out of the dirt at the bottom; or it slides down while shifting from side to side like a skateboarder. It turns out that you can pick out the one way that the ball does get down the hill - rolling along the ground more or less directly - by the fact that that motion has the lowest action out of all the possibilities.

The reason this is so useful in general is that you can describe many different physical systems by making different choices of the rule that tells you how to get from a given motion to the action corresponding to that motion. For instance, if you choose the action to be
$$S = \int\biggl(\frac{1}{2}mv^2 - mgy\biggr)\mathrm{d}t$$
you get Newton's laws for a particle moving in Earth's gravity. If you choose
$$S = \int\biggl(-mc^2\sqrt{1 - \frac{v^2}{c^2}} - q \phi(\vec{x},t) + q \vec{v}(t) \cdot \vec{A}(\vec{x},t)\biggr)\mathrm{d}t$$
you get the Lorentz force law for a charged particle in an electromagnetic field. (I hope that's the right equation - I copied it from Wikipedia but I don't remember enough offhand to check it for typos) And so on... pretty much every one of the major theories of physics (general relativity, quantum mechanics, particle physics, etc.) has a formula for finding the action for a given path. And any new theories or subfields that might be developed in the near future will probably be described in this way as well.

4. Sep 4, 2011

### Mordred

lol I think you mised the part wher he stated he was 14 yars old the answer may be a little over the top lol.

5. Sep 4, 2011

### diazona

No, I noticed. I wish someone had showed me an integral when I was 14 ;-)

6. Sep 4, 2011

### Bobbywhy

mat1101, your question is a good one. One way you could approach the answer is by taking a physics book and studying it completely. I created the below list for a different project. No math, just words. It is not a complete list of all physcial laws, but a place to begin for you.

The Forces of Nature

The Strong force affects quarks in nuclear reactions and is described by quantum chromodynamics.

The Electromagnetic force affects charged particles in chemistry and is described by quantum electrodynamics.

The Weak force affects quarks and leptons in radioactive decay.

Gravity affects all particles and is described by General Relativity.

These four forces mediate all events in the universe. They lead directly to

The Law of Causality

All events have a certain cause, at least to the limits of quantum uncertainties.

The Conservation Laws

Mass, energy, momentum, angular momentum, and charge are always conserved: they cannot be destroyed.

Newton’s Laws

A body at rest or in motion continues at rest or in motion unless an outside force acts upon it.

The acceleration of a body is proportional to the force acting on it and inversely proportional to its mass.

For every force that acts on a body there is exerted an equal and opposite force.

The gravitational attraction between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

Kepler’s Laws

The orbits of our planets are ellipses with the Sun at one focus of the ellipse.

The line from the planet to the sun sweeps equal areas in equal times.

For any two planets the squares of their periods of revolution are proportional to the cubes of their average distances from the Sun.

Einstein’s Laws

The energy of electromagnetic radiation is equal to Planck’s constant times the frequency of oscillation.

The speed of light is constant for all observers and it is the maximum possible velocity.

At relativistic velocities the Lorentz transformations cause length to contract, time to dilate, and mass to increase.

Energy of mass is equal to that mass multiplied by the speed of light squared.

Mass curves spacetime and curved spacetime dictates how mass and energy move.

Thermodynamic Laws

All the heat energy added to a closed system can be accounted for as mechanical work, increase in internal energy, or both.

The entropy of an isolated system not in equilibrium will tend to increase and approach maximum value at equilibrium.

As temperature approaches absolute zero the entropy approaches a constant minimum.

Gas Laws

Boyle’s: At a constant temperature the volume of a gas varies inversely as the pressure.

Charles’: In a gaseous system at constant pressure the temperature increase and the relative volume increase stand in approximately the same proportion for all perfect gasses.

Electromagnetic Laws

Coulomb’s: The force between two charges at rest is proportional to the product of the magnitude of the charges and inversely proportional to the square of the distance between them.

Maxwell’s: Every part of an electric circuit is acted upon by a force tending to move it so as to enclose the maximum amount of magnetic flux.

Ohm’s: The potential difference between any two points in a circuit equals the current times the resistance.

Kirchoff’s: The algebraic sum of the currents entering any junction point in a circuit is zero. The algebraic sum of the changes in potential around any closed circuit path is zero.

Faraday’s: In the processes of electrolytic changes equal quantities of electricity charge or discharge equivalent quantities of ions at each electrode.

Ampere’s: A flowing current generates a magnetic field around it.

Lenz’s: An induced electromotive force tends to set up a current whose action opposes the change that caused it.

Chemical Laws

Proust’s: A chemical compound always contains exactly the same proportion of elements by mass.

Dalton’s: The pressure exerted by a mixture of gasses equals the sum of the separate pressures which each gas would exert if it alone occupied the whole volume.

Quantum Laws

Heisenberg’s Uncertainty Principle: It is impossible to know precisely both the position and the momentum of a quantum particle.

De Broglie’s: The wavelength of the photon’s (or a baseball’s) guide wave is equal to Planck’s constant divided by the photon’s (or the baseball’s) momentum.

Schrödinger’s equation: Describes how the quantum state of a physical system changes in time.

Pauli Exclusion Principle: No pair of identical subatomic particles can simultaneously occupy the same quantum state.

7. Sep 4, 2011

8. Sep 5, 2011

### Bobbywhy

Mordred, thanks, great site, full of useful info. I will definitely use it!

9. Sep 5, 2011

### mat1101

Thanks for all the help everyone!