Units Definition and 975 Threads

Homework Statement What is the volume of one mol of iron where iron is 55.8 g/mol and the density of iron is 7.86 x 10^3 kg/m^3 ? Homework Equations p = m/v The Attempt at a Solution I can get the numerical answer (checked back of book), but I'm not sure how my units worked...

Homework Statement Check that a given momentum space wave function is normalized. I've done the integral, but the result is not dimensionless. Here is the wave function: \overline{\phi} = \frac{1}{\pi} ( \frac{2 a_{0}}{\bar{h}})^{3/2} \frac{1}{(1+(a_{0} p / \bar{h})^2)^2} The units of this...

Hi, Im a studying designer currently working with an engineering CAD program. I have calcualted the mass of the part using an analysis feature in the program. However, I have very little engineering interlect and cannot completely understand the results. The returned result is...

I am looking at some Christoffel symbols that are expressed using geometrized units, and the only variables to appear are m,r and theta. If I want to convert these to non-geometrized units, how do I know where to place the G's and c's? Is there a consistent way of doing this sort of thing...

Hi to all, where can I find specifications (symbol,abbreviation ...) of all units from the systems above ? Wikipedia is not so good for my problem. I' ve found this : http://www.knowledgedoor.com/1/Library_of_Units_and_Constants/Group_Index/acre-foot_group.htm but there is no information...

Homework Statement An air-filled spherical capacitor is constructed with inner and outer shell radii of 7.00 and 14.0 cm, respectively. (a) Calculate the capacitance of the device. (b) What potential difference between the spheres results in a charge of 4.00 microC on the capacitor...

Hi everybody, I have a very quick question about surface brightness profiles for an edge-on galactic disk. I have surface brightness values (V-band, not that it matters) in units of mag/arcsec^2 as usual, as a function of z, which is the distance from the galactic disk's plane. I'd like to...

A general question. A unit element is one that has it's multiplicative inverse in the ring. An element p is prime if whenever p=ab then either a or b is a unit element. Can a prime be a unit element? The answer is, i think, no but thus far I've been unable to find a contradiction.

Hey folks, I'm writing a pop-sci article for a journal and one of the referees wants me to give the cosmological const in mks units instead of GeV. I just wanted to check with anyone in the know if the following looks correct. First, the accepted value of lambda (order of mag)...

Sorry, I think I made a thread in the wrong section before. I was wondering if anyone thought time could have a speed? If so, what would be its dimensions? I encountered someone who claimed that (distance)(speed of light)^2 = speed of time with units, that would be m^3/s^2 = speed of time...

Homework Statement What are the units of solid angle in other systems ( In SI, it is steradian) Homework Equations The Attempt at a Solution

In rotational motion , the units for torque, \tau = r \times F , are N \cdot m and for work done by a torque, W = \int_{\theta1}^{\theta2} \tau \cdot d\theta , are Joules. Yet both these quantities are homongenous/ have same SI units. Is it so wrong to quote torques in...

What will be the dimensions of temperature in a particular second, say the 10th?

Hi all! Homework Statement The problem is: For a particle with electric charge equal to that of one electron, the trajectory radius R is related to the absolute value of the perpendicular component P_{\bot}of the relativistic moment perpendicular to \textbf{B} from the relation...

Homework Statement 1. What is the meaning of Planck’s units? Hint: Compare the strength of the 4 fundamental forces. 2. Calculate the Planck’s dimensions as a function of the SI units. 3. What are the dimensions of the human being in terms of Planck dimensions?Homework Equations Plancks's...

Where can I get a list of standard sizes for I beams? (Preferably in SI units, just to save me time)

If i have a signal S(t) (the plot would be voltage vs time) and I take its Fourier transform, what are the units of the vertical axis? The horizontal axis can either be frequency in hertz or in radians, but what about the other axis? I guess generally I plot the magnitude of the transform since...

I often hear about how solving some problem would require a computer "the size of the known universe", or something like that. Is there a "unit" of computing power? How many units of this power would say a 1cm^3 cube of hot gas have? In other words assuming you wanted to simulate the actual...

Hi, So, assuming the theoretical existence of a monopole, we would have to alter the maxwell equations to give the magnetic field a divergence, and also to ensure that the divergence of the curl of the electric field is still zero we would have to add a term. The altered divergence of B would...

I was working a problem in a Modern Physics book: Find the momentum (in MeV/c) of an electron whose speed is 0.600c. My first approach was: mass of electron = 9.1E-31 kg \sqrt{1 - \frac{(0.600c)^{2}}{c^{2}}} = 0.800 p = \frac{9.1E-31 * 0.600c}{0.800} = 2.04E-22 (ignoring units)...

Sometimes I see V representing Electric Potential. Is this the same as electric potential energy? What are the units for V? Sometimes I see V represent volts. But this just seems weird. V is a unit of V? As an analogy, we use kg is a unit of m (mass). We never use m as a unit for m.

Homework Statement Let g(x) = x^2 + 12x + 36, a parabola with one zero at x = -6. The parabola moves downward at a rate of 2 units/sec. How fast is the distance between the zeroes changing when they are 10 units apart? Homework Equations g(x) = x^2 + 12x + 36 The Attempt at a Solution...

Refractive Index Units - URGENT - Homework Statement Does the Refractive Index of a medium have units. If so what are they? i am needing this for a lab report - so i can quote answers and feel fine that i am not giving any units. I am pretty sure there arent any.

This may be a weird question, but oh well. Way back during the Scientific Revolution it would have been possible to define mass as acceleration divided by force right? Then you'd have F = a/m, and the units for force would be different than they are now.

Im just curious what the units are for coulombs and volts in m kg and s.

[SOLVED] squaring units Homework Statement When you calculate numerically something like q^2/4*Pi*Epsilon_0, do you square the units of q i.e. is it (q 1.602 176 487 × 10-19 C)^2 or q^2 1.602 176 487 × 10-19 C ? Homework Equations The Attempt at a Solution

Show the quantity volts squared per ohm (V^2/ohm) has SI units of power. P = V x I where P is the power (watt or W) V is the potential difference (volt or V) I is the current (ampere or A) From Ohm’s law I = V / R where R is the resistance (Ohm or Ω). So...

"quantum sensor" and units issue I'm working on an wireless sensor network for a commercial greenhouse concerned with energy use and efficiency. Much of the literature regarding photosynthetic active radiation uses watts/square meter, but the client has requested a measurement in...

[SOLVED] What are the standard units for inertial mass and gravitational mass? 1. What are the standard units for inertial mass and gravitational mass? And also apparently gravitational mass can be measured without gravity how can it be done? Thank you very much. My teacher said a hint is in...

I've just been introduced to wavelengths and so forth in my Physics class but i was out for 3 weeks and I'm basically expected to do all these equations and homework with no help or anything. Can't contract my professor, it's winter break and I've tried researching but i can't find what the...

If The second is currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom. And The meter is defined as 1⁄299 792 458 of a light-second. Then Why can't we...

I'm currently putting together a basic summary of the Lambda-CDM model and I have a slight issue with the fact that the equation to calculate lambda (which includes factors to convert physical units into geometric units) is incorporated into the omega_lambda calculation (which incorporates the...

Homework Statement What are the units of angular velocity of precession? I've looked evrywhere and can't find out. Homework Equations The Attempt at a Solution In my answer to a question, by putting units into the equation i think I am getting units as rad^-1 s^-1 but not sure...

Homework Statement The units for weight are A)kg B) Newtons c) kg(m/s^2), the 2 means squared d) both b and c Homework Equations The Attempt at a Solution i believe the the answer is d am i right?

a) What is the modern definition of the time unit and the length unit? b) How people actually Materially realize these units ? (a) in the wiki, it reads: Second: Under the International System of Units, the second is currently defined as the duration of 9,192,631,770 periods of the...

I *think* this is right, but if there is something obviously wrong please tell me where Ive got a mass of weight 'y' dropped onto a surface that can support 10y there is no wind resistance the mass starts from stationary and accelerates under gravity (assumed to be 9.8 m/s/s) the...

Hi I have a question about the common unit for the intensity of a synchrotron X-Ray spectrum: \frac{Photons}{sec*mrad^{2}*0.1\%BW} I am not sure how to interpretate the 0.1%BW. How do I get the numbers of Photons/sec/mrad2 in an Energy range lets say from energy E_1 to energy E_2...

I have a problem with units... I have been looking at energy loss of muons in matter (from both ionizations and radition processes like bremsstrahlung). I have used an equation for the mean energy loss (for a muon of specified energy in a specified material) which gives an answer in units of...

Can work be expressed in the units lb times lbf?

Hi, This is my first post, so hello everyone! I just have a quick question about the k-calculus, and am using the 2nd diagram on http://www.geocities.com/ResearchTriangle/System/8956/Bondi/intro.htm as a reference since it is the same one as in the book i am reading from. In the...

Finally after man(and woman)fully resisting the urge to go fully metric for 30years the UK's boffins have produced an alternative system of units, even more brilliant then the venerable Firkin/Fortnight/Furlong system. The velocity of a sheep in a vacuum is 26.22 kilobrontosauruses per...

Homework Statement What are the units of the probability flux j? \vec j = \frac{\hbar}{2mi}\left(\Psi^* \vec \nabla \Psi - \Psi \vec \nabla \Psi^*\right) Homework Equations The Attempt at a Solution The units of psi are probability amplitude and the units of del(psi) are...

Hi, when someone gives me an angular frequency in units of inverse length (i.e., 520.5 cm^-1) how do I convert that to a frequency and and energy (say, in eV?). Thanks for the help!

hey can anyone give a calculator(like any html link) or something of that sort which can convert units, like from british system to SI units and vice versa. looking at the tables everytime is sooooo boring and i am fed up of it.for eg. changing lengths, pressure, weight etc. etc.:-p:-p

Homework Statement Which of the following definitions or units apply to pressure? True False Newtons per square meter True False kg per cubic meter True False pascals True False force per unit area True False mass per unit volume The Attempt at a Solution My answers are in...

What's the differences between Radiometric Units and Photometric Units?

This isn't an actual problem in my text so I won't be using the usual template to ask it, just a quick clarification question: According to a chart in my text, a micro is 10^-6. So if I had, say... 20 micrometers of something and wanted to convert to meters... wouldn't that just be 20E-6 meters?

I've just completed a question using Bernoullis equation but I am unsure of what units I should give the answer in. By taking the units of the terms in the equation to be Pressure density velocity density acceleration height Nm^2 Kg m^-3 m s^-1 Kg...

When you solve a problem and it wants the answer in non-SI units and they given you non-SI units, do you need to convert the non-SI units to SI units before you plug them into equations such as x=1/2gt^2. If you don't convert them into SI units, you'll get the answer wrong right? Basically...

I was bored so I make fun with derivations of SI units of many Physics formulas. Note, this should just be called "introductory physics", that means NO calculus (but rate of change designated by the delta symbol) and motion is in one or two directions only. This is high school physics level in...