quantities Definition and 208 Threads

The title pretty much says it all, but let me elaborate on the source of confusion. VIM defines quantity as: Other definitions I found are extremely circular. They typically go like this, "a physical quantity is a property that can be quantified". In other words, they explain quantity with...

Homework Statement Find two independent conserved quantities for a system with Lagrangian L = A\dot{q}^{2}_{1} + B\dot{q_{1}}\dot{q_{2}} + C\dot{q}^{2}_{2} - D(2q_{1}-q_{2})^{4}\dot{q_{2}} where A, B, C, and D are constants. Homework Equations None.The Attempt at a Solution I've only found...

http://img842.imageshack.us/img842/7200/img0103iu.jpg Mainly concerned with the first half of the page. You'll see that it derives for a system in contact with a constant-temperature, constant-pressure heat bath that the change in Gibbs entropy is always less than or equal to zero. Equality...

What are the difference between extensive and intensive quantities?

Hi, I am not a chemist but maybe there is somebody who can help me. I need a put together an emergency plan as part of a college law assignment on European Seveso directives. My case study has 17t of Hydrogen and 8t of Fluorine. Both of which combine satisfy the requirement for a lower...

Hello, Of the different rotational quantities of motion--angular velocity, angular acceleration, torque, angular momentum, etc.--, which of them has their direction perpendicular to the plane of rotation (not sure if I worded that correctly)? I am pretty certain that torque has its...

Need help differentiating multiple quantities Homework Statement f′(x) = (x − 1)(x − 2)^2(x − 3)^3(x − 4)^4(x − 5)^5 I need help in trying to differentiate this equation. I know could use a combination of the chain and product rule to figure it out, but my teacher said that doing so would...

Homework Statement Fill in the missing quantity for the following: V = constant FNet = ? a = ? F1 = ?Homework Equations FNet = Fn - Fg + Fa - FF Fg = mg FNet = maThe Attempt at a Solution Because I honestly do not know how to go about solving this, the only things I've done are review class...

So having been through translation and rotation I can conclude that my book has found 3 conserved quantities in classical dynamics: Energy Angular momentum Momentum That is 7 separate quantities which are conserved E,Lx,Ly,Lz,px,py,pz But this question is bothering me: How do we know that...

Hi All PF Members... I'm New to this website.. Also new to physics... nd I'm very exited about this aweSome website...where I can post my problems... Experts I want list of All physical quantities and their Dimension... I've been searching and cannot find any thing good enough... Sorry for my...

Adiabatic process: a process where no heat is gained or lost. it is my understanding, however, that this is a hypothetical system. There is no insulator on Earth good enough to allow this system to exist, except to approximations. So, what happens is you have a system where whatever is...

Homework Statement This is actually a part of my physics lab assignment, but there isn't any physics involved here, so I chose to post this here. I hope that isn't a problem. Anyway, I've been given three data tables, and have been asked to make graphs for each of the data tables by hand...

Hi, I'm a new AE Ph.D. student in the field of supersonic mixing and combustion, currently making preparations for ordering equipment necessary to perform Filtered Rayleigh Scattering measurements in our tunnel. At this point, I am implementing a model for predicting the shape of the...

Hello, Can Someone help me with this activity - http://www.particleadventure.org/other/education/five_s.html - its activity 5 The rules of the Game The answer to the activity is - http://www.particleadventure.org/other/education/five_s.html I don't understand how they got the answer for...

How can we distinguish scalars from vectors?If we are given a certain physical quantity how can we justify whether it is scalar or vector?

Firstly, my question is - why do we use dimensionless quantities? Next question, I would like to know the physical significance of Nusselt number, Prandtl Number, Sherwood Number, Scmidt Number, Peclet Number and Gratez Number! Thanks in advance!

When you write vector quantities with unit vectors, do you still have to draw an arrow on top to indicate that it's a vector? e.g. velocity and acceleration. My textbook doesn't have it bolded so does that mean they're just taking the magnitude and then multiplying by the unit vector to make it...

Consider the velocity vector v^i=\dot{x}^i \hat{e}_i . We know that in the plane polar coordinates,it becomes \vec{v}=\dot{r}\hat{r}+r\dot{\theta}\hat{\theta} We also know that it is a contravariant vector so if we transform it covariantly from cartesian coordinates to plane polar...

In Physics it seems quantities are either Scalars or Vectors (let's not get into tensors, but if there are other types, please tell me). Vectors I understand reasonably well. Scalars, however, I'm not so sure about: Consider the Scalar quantity of Temperature. There is absolute zero, but...

Why are pure numbers like 1 , 2 , 3 ... dimensionless and Avogadro's Number, Plank's Constant, Gravitational Constant dimensional ?

My question is at the bottom of this post PREAMBLE: If a dipole is turned by an angle θ (in a uniform electric field) then the torque applied on the dipole by the electric field will be: τ = 2.q.a.E.sin(-θ) = -2.q.a.E.sin(θ) with the negative sign referring to it being a "restoring" torque...

I've been doing some amateur simulations of particle trajectories in a few well-known metrics (using GNU Octave and Maxima), and in the case of the Schwarzschild and Gullstrand-Painleve metrics I have the ability to check my results using freely available equations for conservation of energy and...

Symmetry, Groups, Algebras, Commutators, Conserved Quantities OK, maybe this is asking too much, hopefully not. I'm trying to understand the connection between all of these constructions. I wonder if a summary about these interrelationship can be given. If I understand what I'm reading, there...

Hey, atm I'm working on a physics project for school where we pick an instrument and answer questions about it that we'll have to present in class. I'm going to use a drum pad. The one question I'm stuck on is: I'm not sure if this would be right but please correct me if I'm wrong: For...

Is it because measurement of those quantities involves action on the system. And is the idea that as light is to be used to measure momentum which effects its position fundamental of QM or is it merely like an analog to understand.

The DE is Insect Outbreak Model: Spruce Budworn with Ludwig's predation model \frac{dN}{dt}=r_BN\left(1-\frac{N}{K_B}\right)-\frac{BN^2}{A^2+N^2} r_B is the linear birth rate K_B is the carrying capacity The last term is predation A is the threshold where predation is switched on...

How can I see that the generators of the Galilean group correspond to energy, momentum, etc.? References which cover the Galilean group and algebra as well as their realization in phase space are appreciated, especially if they are not too sophisticated. Thanks kith

Hello I know that it's possible to reformulate Newtonian mechanics in such a manner that absolute velocities of objects can be defined. By absolute I mean defined without any reference to a specific frame of reference (just as in the article Notes on Mathematical Physics for Mathematicians)...

what is the most important fundamental quantity

Hi:) A question that I don't understand, and my feeble attempt to answer it. Can anybody give any heads up on this one? If a physical quantity is dimensionless, it has no units attatched to it. Determine if the following constant is dimensionless and show your reasoning" \alpha=...

Homework Statement K(max) = (6.63x10^-34 J s)(7.09x10^14s) - 2.17x10^-19J solve for kmax Homework Equations none? The Attempt at a Solution K = (6.63x10^-34 J s)(7.09x10^14 s) - (2.17x10^-19 J) K = (6.63)(7.09)(10^-34)(10^14) J s^2 - (2.17x10^-19 J) K = (47.0067)(10^-24) J s^2...

I've seen that in English you refer to the measurable physical properties as http://en.wikipedia.org/wiki/Physical_quantity" , but some sites call them "physical magnitudes". Are both of them correct?. Do you consider them as synonyms? In Spanish we say "magnitudes físicas", and I wonder if...

Hello everyone, My general goal is to understand why and how certain physical formulas came to be written, a specific way and not another - so as to judge their correspondence with reality. My specific interest in this thread is to understand the link between a formula(calculated or complex...

"Small" quantities in mathematica Hi, I'm doing a calculation in which I have a small parameter \epsilon floating around, and I want to automatically remove terms of order \epsilon^2 and higher. Is this possible to do?

Hi, I have a little problem, I'm using a code to run cosmological simulation and I have to recover the physical unities of every quantities. The problem is that there isn't a proper guide for this program. I try to explain. All I have for every output/redshift is: aexp unit_l unit_t The...

Homework Statement Exactly the same problem as https://www.physicsforums.com/showthread.php?p=3335113#post3335113 but instead of a cylinder, the surface is a cone.Homework Equations Same as previous thread. The Attempt at a Solution I used cylindrical coordinates (r, \phi , z). By intuition I...

Homework Statement I must determine the conserved quantities+the equations of motion (of the trajectory in fact) of a particle over the surface of a cylinder.Homework Equations Lagrangian and Euler-Lagrange's equations.The Attempt at a Solution I've found the Lagrangian of the particle to be...

Homework Statement I need to solve a task which requires to calculate the quantities of graphite. For instance, the particle amount per emission. I think my calculation may use the wrong method/ formula, but I do not know alternative right equation. The data available: graphite granularity...

Homework Statement I am given the first human chromosome as a long list of bases: ATGCCTGC... (I have N bases) I have to divide the the chromosome into subsequences of length L, so subsequences are as follows: From base 1 to base L From base 2 to base L+1 From base 3 to base L+2 ... From base...

Homework Statement -Find the sum of the two quantities: Y1=sin(Wt) Y2=sin(Wt+30 degrees) Homework Equations Y(x,t)=AsinK(kx+Wt) <------- not sure if this is relevant W=2(3.14)f , where f=frequency The Attempt at a Solution sin(Wt) + sin(Wt+30) = sin(Wt) + sin(Wt) +...

I'm really confused about invariant quantities.Could someone explain which quantities are invariant in special relativity and how are they recognised? thanks

Which quantities are "naturally" forms, and which are (multi)vectors? I'm undertaking a self-study of geometric algebra and differential forms. It is very enlightening, but I find I'm getting a bit confused by which kind of beast is most "natural" for a particular physical quantity. Where...

What is the implication of the fact that quantities like electric charge, color etc are conserved not just globally but in local region of space too? I understand the later is more restrictive but what advantage does it offer?

I'm currently reading Griffiths book (I'm at chapter 4) on Particle physics, and I had a question about Feynman diagrams. In every "node" of a Feynman diagram, what quantities are conserved? Further, what quantities are conserved over the entire diagram?

Does assuming time and space are quantized quantities make predictions of quantum physics more accurate? I have heard about the "Planks time" but do not know whether its is really a concept in quantum theories.

Hi all! I came across 2 questions on my course work, and i don't know what is required here, can some one help please? Q.1 Define the common derived units of the following physical quantities; and express them in terms of the base units: Mass, Length, Time and Electric charge (or Electric...

Hi, Please see the attached document. In a simple calculation, I am trying to add the cash flow per share of two companies. I think I am doing something wrong as I am not able to reconcile the results of this calculation to the actual results. Can you please take a look? Thanks, MG.

Hi everyone, have a question about covariant, coordinate independent quantities in GR. Reading Kolb and Turner's book The Early Universe one can find the Boltzmann equation in a GR setting. Now, one of the terms in that equation is - \Gamma_{\alpha \beta}^\gamma p^\alpha p^\beta...

Homework Statement A golfer rips a tee shot from an elevated driving range tee-off such that the ball leaves horizontally. The ball lands exactly at the 66.8 meter marker, and was shot from the upper level (6.5 meters above the ground). How long was the ball in the air? And how fast did...

Homework Statement Determine whether each statement below is True or False. 1. T/F Single vectors may be represented as pairs of vector components. 2. T/F Vector quantities are completely described by magnitude only. 3. T/F A scalar quantity requires both magnitude and direction for a...