Units Definition and 976 Threads

Conduction - Heat Equation - Units Don't Add Up! Hi there I have what I think/hope is a simple question: I've been working on heat inputs and outputs in inertia friction welds and have managed to produce a net power term (W) as a function of time. I now want to use that in the heat...

Homework Statement My book says that each term in the Bernoulli equation (when divided by ρ, has pressure units). I don't see how. Homework Equations The Bernoulli equation for steady, incompressible flow is: \frac{P}{\rho}+\frac{V^{2}}{2}+gz=constant The Attempt at a Solution...

Hi all, I am building a model in Abaqus and wondered if somone could assist with the units I need to enter. I have built my parts using mm as the dimension, i.e. part is 10 units (mm) wide. (To clarify this can also be entered as metres as in 10e-3, however I chose to be consistent with...

I'm having some difficulty in working with units of mass at the quantum level. This difficulty most clearly manifests itself when I'm doing a Compton scattering problem. Recall that Compton scattering is given by \Delta \lambda =\frac{h}{m_{e}c}(1-cos(\theta )) and that the rest mass of an...

Information Theory - Shannon's "Self-Information" units Hi, I'm familiar with information and coding theory, and do know that the units of Shannon information content (-log_2(P(A))) are "bits". Where "bit" is a "binary digit", or a "storage device that has two stable states". But, can...

Hello, I'm just wondering is it possible to put the units of a parameter underneath it rather than next to it. My table is pretty long and I could free up space if I could do this. For example, let's say I have Velocity (m/s) I want it to have (m/s) below velocity I can't figure out how to...

Homework Statement Hello everybody, Can you help me solve this: Coal-burning power plants convert the sulfur in the coal to sulfur dioxide (SO2), a regulated air pollutant. The maximum allowable SO2 emission for new power plants (i.e., the maximum allowed ratio of the mass of SO2 emitted...

Hi guys. I have been a mathematical physicist and have recently been taking great interest in theoretical particle physics. With some effort I can do calculations in the International System of Units (SI) with complete success if I focus very carefully. With the particle physics natural units...

Homework Statement Let R be a ring with multiplicative identity. Let a, b \in R. To show: 1-ab is a unit iff 1-ba is a unit. The Attempt at a Solution Assume 1-ab is a unit. Then \exists u\in R a unit such that (1-ab)u=u(1-ab)=1 \Leftrightarrow u-abu=u-uab \Leftrightarrow abu=uab. Not...

Homework Statement Let R be a ring with multiplicative identity. Let u \in R be a unit and let a1, ..., ak be nilpotent elements that commute with each other and with u. To show: u + a1 + ... + ak is a unit. The Attempt at a Solution Need to show that u'(u + a1 + ... + ak)=1 for some u'...

When solving with E=mc^2 what units should I use in the answer?? For example: (if I have an object with a mass of 43kg) E=mc^2 E=(43kg)(299792458m/s)^2 E=3.86464727 × 10^18 Now here's my problem, do I include units of J/kg (joules per kilogram) or eV (electron volts)?? If someone could...

Homework Statement I'm plotting a man jumping over a car for maths and I'm trying to find the critical velocity at which the car has to travel for the jumper to make it safeley over the car the man's jump is approximated by the parabola y= -0.0176x^2 + 0.3595x - 0.2794 and restricted by the...

Hi everyone, in the book of Paul Harrison (Quantum Wells, Wires and Dots, 2nd Ed.), it is said that \hbarω=871.879 meV but it is known that \hbar=6.58214928\times10^{-13}meV so i can inferred that \omega=9.9879927, but i don't know the units of \omega, or how can i deduce what units he used for...

If I had a value of 6V and then found the log which is 1.79 (3.s.f) what are the units of this quantitiy? or is it dimensionless? why?

I'm trying to do a calculation using: Heat transferred = mass x specific heat capacity x change in temperature q=mc∆T But the value I'm trying to calculate is the change in temperature so I've rearranged the equation to ∆T= q/mc I think the numbers and answer I have are correct, but the...

Hi all, I have a spreadsheet which says failure will occur in my composite piece when a load of 3500 lb/in is applied. If I were to tensile test this piece and the thickness has already been input (0.138 in) does this mean for every inch wide the piece can take 3500lb of force? That seems...

Hello, I am in Grade 12 physics class and I have been given a open ended project; where we are required to build/create a machine which would involve at least 6 of the physics concepts: ramps, pulleys, levers, transfer of momentum/energy, projectile motion, circular motion, stored elastic...

Homework Statement Let the Hamiltonian with canonical variables be H(q,p)=\frac{\alpha ^3 e^{2\alpha q }}{p^3} where alpha is a constant. 1)Given the generating function F(q,Q)=\frac{e^{2\alpha q }}{Q}, find the expression of the new coordinates in function of the old ones: Q(q,p) and P(q,p)...

I have a physics project, but how do I express the uncertainty of a dimensionless quantity? E.g. how do I express the uncertainty of the coefficient of friction? Do I just write 0.403 ±0.02?

Hello there, I am reading this article: http://nis-lab.is.s.u-tokyo.ac.jp/~nis/cdrom/sig93_nis.pdf After chapter 4.2, it mentions some equations for approximating Rayleigh scattering. That is all well, however, it doesn't mention which units of measurement I should use, nor the value of...

Homework Statement My problem is to determine whether or not my conversion is correct. 2.00 g/cm^3 is = _______ kg/m^3 Homework Equations If I'm not mistaken, 1 cm^3 = 0.000001 m^3 1kg = 1000g The Attempt at a Solution My equation: 2.00 g/cm^3...

Ok for the life of me i can't remember how you get from say 15 miles per hour (15m/h) to 15mh-1?

I'm a little confused about the conversion between lbm and lbf (mass pounds and force pounds). I'm doing a problem where I'm using Newton's 2nd law to calculate mass flow rate. F= Δ((Mass flow rate)*Velocity) I know my force is 400 lbf and velocity is 40 ft/s so mass flow rate is...

I'm having some troubles understanding the unit used in solid state physics. In a paper I read \Lambda a \sim 1 where \Lambda is a momentum cutoff and a is the lattice spacing of a crystal. Questions: 1) What kind of units are customarily used in solid state physics scientific...

See the arrow in the jpg file. There must be a unit missing somewhere, since a is distance, and is used as the sqrt(a).

I was wondering what were the fundamental physical units of measurement, ie those from which all other units can be derived. To my mind, there are only two things which exist in the universe and from which all units of measurement can be derived : space and matter. The reasoning is as follows ...

Homework Statement I just want to be 100% sure I got this correct. I have a log graph, and along the x-axis I have diameter (in cm's) and up the y-axis I have period (in seconds). I had to get the slope, which I got, but what are the units of the slope? s/cm ? Homework...

What is g_c in pound force. It is said that it is dimensionless It says in my book that in america where they measure acceleration in feet per s^2 we have: 32.1740 \frac{lb_m\cdot ft}{lb_f\cdot s^2} then they say in my book that in SI-units we get: g_c=32.1740\frac{0.453593 kg...

According to my teacher in my chemistry lesson, the equilibrium constant has different units depending on how many moles of reactant and product there are. But the idea of a constant which changes it's units depending on the situation seems a bit dodgy to me, especially as it seems to be related...

For some reason I can't seem to be able to convert units without getting all mixed up. I can convert feet to inches to cm fine, but I can't convert units in a more complicated problem; for example, converting ft/sec to km/hour. I just get really mixed up and lose track of the numbers. ] I...

Homework Statement A large school district has 300 school buses. If each school bus is used 3 hours each day, the average speed of the school buses is 15 mi/h, and the fuel economy of the buses is 10 mi/gal. How much does it cost to run these buses in 22 school days if gasoline costs $1.20 a...

Homework Statement Let R be a commutative ring with 1. What are the units of M_n(R)? Homework Equations N/A The Attempt at a Solution If R is a field, then I know that we can characterize the units as those matrices with non-zero determinant (since those are the invertible...

What are gravitational units?? My teacher recently taught us about gravitational units... she said that its the absolute unit multiplied by acceleration due to gravity... I did not understand the significance of this...Please help me

Homework Statement Hello. I have a small question... How does one correctly "modify" an equation to work in different units? The equation below gives the boiling temperature of isopropanol as a function of pressure: T = B / (A - log10P) - C Where T is in kelvin, P is in bar, and A= 4.57795...

Homework Statement If speed, v, of an object depends on time, t, according to the equation v = A + Bt + Ct^4, what are the SI units of A, B, C? Homework Equations v = A + Bt + Ct^4 The Attempt at a Solution For this, I've not known where to start, so I've be plugging in the variables...

What are the advantages to using one system to measure an angle over another. For example why do we measure angular velocity in radians instead of degrees? Are there any intrinsic advantages to one unit over another? Thanks AL

Hi, What happens when, following a numerical calculation, you have to prove the units but the equation has logs? For example: ln P = (ln z1 - ln z2)/(z1 - z2) So as the RHS will simplify to a number when all values are known you end up with: ln P = x, x being some value so to find P you...

Hi, I am hoping that someone could enlighten me about pipe schedules. I've searched online but there have been conflicting definitions for schedules, where some people refer to it as pressure and some referring to it as thickness. I need a pipe to be able to withstand 70bar of pressure...

Coulomb's constant, which appears in Coulomb's Law, contains ε0. The units of ε0 being F/m Are the units of Coulomb's constant therefore F/m ? Thank you.

Definition: Let R be an integral domain. A nonzero, nonunit element r in R is said to be irreducible if whenever r=ab, then a is a unit or b is a unit. My question is are units considered irreducible. This how I understand it, Let v in R be a unit such that v=ab ==> 1=ab(v^-1) ==>...

Okay, so I have an expression for V(R) in atomic units (bohrs, hartrees, etc), where V is an energy. I'm assuming this means that if I plug in a value for R (in bohrs), I get back an energy (in hartrees). But if I take the SECOND derivative of V with respect to R, and I want to convert that to...

In "Classical Theory of Fields", by Landau & Lifgarbagez, they give, for example, the force on a charged particle by a magnetic field as: F = \frac{ev}{c} x H where H is the magnetic field intensity. Now, normally written in SI units, this expression would use B and no factor of 1/c...

In Hartle's book on General Relativity, page 47 footnote 1, it says: "You might be used to thinking that quantities called \epsilon_0 and \mu_0 are the basic parameters in Maxwell's equations, but \mu_0 \equiv 4\pi \times 10^{-7} is a pure number, and \epsilon_0 = 1/(c^2 \mu_0)." But as far as...

In an example in my algebra text, (from the section on unique factorization domains) it is describing the ring \mathbb{Z}[\sqrt{-5}], and demonstrating that it is not a UFD. It starts by giving the norm N(a+\sqrt{-5}b)=a^2+5b^2. It remarks that if zw=1, then N(z)N(w)=1, and then it goes on...

I am having a problem finding the correct SI unitsfor the quantity A? In the equation A=√(R/TY) That is A equals the square root of R divided by TY (not to good showing workings on the computer sorry) , the SI units of the quantity R are kg m^3 s^–2, the SI units of the...

I came across this question. Is the group (ℤ/34/ℤ)x cyclic? We haven't discussed the theorem in class that any units group of Z modulo n is iff n = 1, 2, 4, pk and 2pk (where p is an odd prime). But thanks to Deveno I know about it. So in this case, p =17 works, so the group is cyclic? but is...

Homework Statement I want to find a relationship between the number of moles of O2 used and the number of CH2 units in an alkane in a complete combustion reaction. Homework Equations The Attempt at a Solution Right now I have come up with a math equation, given X units of CH2...

1. I am doing a lab about solar radiation. We collected data using a lightmeter which measures illuminance in lux. Now to calculate the optical depth of the atmosphere I either need to find an expression for the solar constant in lux or be able to convert illuminance values in lux to W/m². The...

I was flipping through a physics text and some of the units seemed pretty 'crazy'. Just wanted to know if they can always be understood intuitively, like you can visualize what's going on e.g. force, mass x acceleration, if I look at it as kg*m/s^2 then it doesn't really make sense to me...

Hopefully this is a really simple question to answer. A problem I have uses the following information: The specific heat of air = 1.05 kJ/hg-C. Does anyone know what the hg-C stands for? I know specific heat is usually expressed in terms of J/C, so this is confusing me.