Units Definition and 998 Threads

i just need help with finding the units to a physics problem at the end. some examples... \sqrt{\frac{940N/m}{0.038kg}}*(0.25m) it comes out to 39m/s. i know that since it's velocity, it should always be m/s. but there are some question that i don't really know what the final units...

I am interested in a system of natural units that I see used more and more frequently in Quantum Gravity research papers so I like to try using them. the units are like conventional Planck except |8piG| = 1 I want to see if there is anything in the Cambridge Handbook of Physics Formulas...

Hi. Part of my homework was to work out what the SI base units of the gravitaional constant are. I'm crap at working out base units so could somebody help me out? Thanks If anyones wondering, G is 6.67 x 10ˉ¹¹ N m² kgˉ²

Let's say i have some function S(t) where t is in seconds and S(t) gives feet per second. As I take the derivatives of S to get the acceleration function, why is the feet unit squared? What's the best way to conceptualize what's going on?

Hello, I am having some problems with converting experimental data to SI units. In a SQUID I measured a magnetic sample and the saturation magnetization is, let's say a. Let' s take the volume of the sample V (cm^3) According to a lot of conversion tables I should get: (4*Pi) *...

Locus help please Just started this unit and don't have a clue as to what is happening. Here is the question Describe the locus points that are 3 units from line y = 2x – 3. Give the equation of the locus. Draw a diagram as well. Well I did a rough sketch of the line given and...

physics momentum problems Fred (mass 70.0kg) is running with the football at a speed of 4.70m/s when he is met head-on by Brutus (mass 130kg), who is moving at 8.10m/s. Brutus grabs Fred in a tight grip, and they fall to the ground. How far do they slide? Part A The coefficient of kinetic...

This is a quick graphing question. We have to graph Vout/Vin versus the log of frequency. Now the Vout/Vin would have no units but what about the log of frequency? Is it hertz or is it also unitless?

Starting fromthe equation \alpha=a/d with \alpha in radians and a and d in meters, show that the equation is also valid if \alpha is expressed in arcseconds, a is in AU and d is in parsecs. Would this be the proper way to show this? \alpha=a/d radians=meters/meters 4.8481*10^{-6} radians...

codons aren't basic units of the genetic code right? my friend told me that it does but i remember in lecture that proff said it doesn't but maybe i misheard

Alright, let's be real here Electrons are ejected from a metal surface with speeds ranging up to 4.71×105 m/s when light with a wavelength of lambda = 628 nm is used. What is the work function (in eV) of the surface? Alright, money, using the formula: Max Kinetic energy = hf - Eo where...

Units -- Watts, meters & Kelvin I have an equation: L = \sigma T^{4} * 4 \pi R^{2} Which I fill with values and units L=5.67*10^{-8} * (5860K)^{4} * 4 \pi * (6.96*10^{8}m)^{2} and I get an answer: 4.07*10^{26} K^{4} m^{2} The correct answer is: 4.07*10^{26} watts I don't...

velocity = 0.5 m/s radius = 1 m \omega = \frac{v}{r} \omega = \frac{0.5 m/s}{1 m} the meters cancel and I'm left with \omega = 0.5 s But \omega is supposed to be expressed in radians/s How do I get those output units with the given input units?

How do I convert 2.07*10^-15 Wb in MKS units into SI units? James

I am currently taking a Unit Operations course. The book and the instructor both refer to a unit, g mol (gram mol). The book defines molarity as 1 (g mol)/Liter. I am familiar with molarity but always in the past it was defined as mol/Liter. I do not understand what this unit is...

Consider : E = \int P(\tau) d\tau = \int A\delta(\tau) d\tau E is in Joules and P(\tau) is in Watts, what are the units of A? What about \delta? I have a hunch, but need to have all doubts removed.

It can be useful to construct and try out alternative systems of units---mind-broadening and you can get a different perspective on physics. And in several specialties they do this anyway because it is almost a precondition to being able to think. Whether QFT or Gen Rel they all have their own...

In the Halliday-Resnick textbooks, there is only mention of strength of a magnetic field, which in SI units is the derived unit Tesla. However, on my TI-89 and on more modern sources on the internet (including a Fuji-film PDF!), there is mention of the unit of the Oersted for magnetic field...

I was reading about the Planck units, and they said that Planck came up with them before his quantum theory of blackbady radiation, and before the constant h had been discovered. They said it's unclear how he found these units. This seems pretty weird to me. How did he come up with these...

Hi all, Sometimes I come across the units of mg/Nm3 for gas concentrations. What I would like to ask is why we need to specify that we are talking about mg per Normal cubic meter? Why not just mg per cubic meter? Whatś that Normal for? Thanks in advance. Billy_w

Hello out there! I'm a new guy here, so don't pick on me too much...I cry easy :wink: I want to show that a set of units in a ring forms a group under multiplication. What steps would I take to show this? Things that my feable brain knows: 1) if a is a unit, it is invertible and...

What does (kg)(m/s^2) = what unit? also does 1 cm^3= 1 mL? i forgot all these units stuff its really bugging up my mind

Here's my problem: Measured data for pressure versus volume during the expansion of gases within the cylinder of an internal combustion engine are given in the table below. Data Point p (bar) V (cubic cm) 1 15...

So here is an example of what I am trying to do. We know that div of an E field=p/eo where p=charge density and eo=the permittivity of free space. This equation is expressed in MKSA units. In order to convert this into Gaussian units, we must multiply E by 1/sqare root of 4*pi*eo, and...

Here's my question: Starting from Coulomb's law, show that e^2/(4*pi*epsilon_0) has dimensions of energy times distance. Coulombs law is F=(1/(4*pi*episilon_0))*(q1*q2/r^2) I understand how to convert the units for e^2/(4*pi*epsilon_0), where e is the charge of the electron, to ev * nm...

we could have a thread for talking about Planck units and getting accustomed to them Planck units are basic and everpresent in QG so it helps to develop a feel for them even tho LQG is itself based on a continuum the underlying spacetime is a continuum and it is only the geometric...

What is the experimental system used to determine that an electron has a mass of 0.511 MeV/c*c ? I'd like to learn about methods other than Millikan's oil drop and Thomson's charge/mass ratios. What is the modern way to generate a value with those units?

Google has a neat calculator built into its search box. There is a good summary here: http://www.google.com/help/calculator.html Copy and paste the following queries to see it work: Arithmetic operations: sqrt((3*6/9)^2+7!) Transcendental: 3*sin( 54 degrees ) 2*log ( e / pi )...

If you guys can check the math on these last 3 questions I would be very greatful. Sorry to throw this many questions at you but I've been doing physics 3 days straight now reviewing for my final tomorrow. Any help would be awsome. :approve: 1. How much heat energy is required to convert a...

In my physics class, when we involved friction...the book kept making it a point of "why the coefficient of friction has no units"...the answer was always because it was a ratio. Well.., if F_{friction}=umg then u=\frac{F_{friction}}{mg}, right? So why can't we say that the coefficient of...

How can I show that if \frac{a}{a^2-2b^2},\frac{b}{a^2-2b^2}\in \mathbb{Z} then a^2-2b^2=\pm 1? If you care to see the whole problem, you can find it here: http://www.math.rochester.edu/courses/236H/home/hw12.pdf It's #4 part c. BTW, why is the significance of this "norm map"? I...

Please can someone explain to me how you convert: 10 micrograms per decilitre into miiligrams per litre I think I had some notes on it somewhere but they have gone awol !

would you give a measurement of mometum units? like kg*m/s?

Just wondering how many people here use English units as opposed to Metrical ones. That is, people living in the english world (UK, USA, Australia, Canada etc) Also, in your dealings with either English units or metrical ones, what have you found to be the major shortcomings of the system?

Hi, I got a simple question, "dot product" have units? I mean, if A=(Ax+Ay+Az)N and B=(Bx+By+Bz)(cm/s) , the units of A.B will be N.(cm/s) Thanks, Cali

What units in the physical universe are not arbitrary? E.g. time (as measured in seconds and years) is arbitrary since it's based on the changing orbit of this little planet in some odd solar system on the edge of an insignificant galaxy. Atomic mass is arbitrary since it relies on which...

The National Inst. of Standards and Technology NIST has a fundamental physical constants website http://physics.nist.gov/cuu/Constants/ and until sometime this year what they posted were the 1998 CODATA recommended values (same as those in Physics Today August 2000, or the CRC Handbook of...

Hello, I'm new here. I was wondering if anyone could help me out with some confusion regarding units. My landlady (like most people) wants to save money on power consumption, so she has me installing Compact Fluorescent Lightbulbs(CFLs), which are supposed to save energy. On the package, it...

What the conversion for bar so that I can use it to work out volume and temprature? Whats the units?

I’m installing a central vacuum in another house I just purchased. I’m not sure what I’ll do with it but a little improvement should make it a good investment. Rather than use a factory power unit, I’ve decided to use 4 shop vacuum units in a series-parallel arrangement. The highest...

sorry I am not sure if this is the correct pigeon hole to use. planck dimentions are well known but why are they the smalest possible units? i think it was wheeler that used Planck units in his quantum foam theory, would we have this theory without planck units?

A pi meson has mass of 139MeV/c^2. what is this in atomic mass? HOw do i solve for this? what steps do I need to do, any examples you can give to help me with to solve? Dx :wink:

Units based on c=G=hbar=k=e=1 turn out to be quick and convenient to use, and one can get used to the scales (a point damgo made earlier in the dimensionless units thread). Heres a kind of minimal toolkit for working with them including some handy comparisons with familiar units. E38 ----a...

If somebody wants to know what Planck units are, how do you go about explaining? Can you make them intuitive without too much technical detail? What would your approach to describing natural units to a non-scientist (possibly a little vague as to what hbar and G are)? I want to know any...

Well, i hate to put silly questions on the forums, but i had to do it this time ! Today i was arguing with my Math teacher on wether it is right or wrong to put equality between two different units. For example, to say that : 1 Metre = 3.4 Foot (i am not sure of the number ... anyway !). I...

I have been playing a bit with the units of coupling constants. Instead of setting c=1, h=1 (natural units) it is interesting to set c=1 but still to keep h explicit in the formulae. You may know that in natural units there is a basic difference between electromagnetism and gravity, namely...

dimensionless cosmology---getting rid of units In cosmology and fundamental physics some papers are written in a system where time, mass, and length are dimensionless. It is not that they are using Planck units---they aren't using any units at all. On usenet recently (sci.physics.research)...

this is not to argue or persuade but just to share a calculation. no answer needed unless you particularly like something about it. several websites, eg. NedWright's Cosmology tutorial have formulas for things like the critical density and the estimate that real density is very close to...