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0
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1answer
175 views

Magnetic Field and the Speed of Light

Is it just a historical choice that both magnetic field and the Lorentz force equation include the speed of light? I figure that whoever wrote up the equations (in cgs!) could have put both factors ...
0
votes
1answer
765 views

CGS Units to SI Units

This may be a stupid question but I am having trouble getting the same result in CGS units as I would if I used SI units for a unitless calculation. I have to calculate $E_c=\frac{m_e c\, \omega_c}{...
0
votes
1answer
960 views

Natural Units and the Nuclear Radius

In a paper I'm looking at and also in a similar program, the authors note that the nuclear radius $R$ is given in "natural units" as $R = 3.11\times 10^{-3}\;A^{1/3}$. This has me slightly confused, ...
0
votes
1answer
116 views

$\mu$T in to $\frac{W}{m^2}$ (for interpreting EMF readings)

I am considering purchasing an EMF reader, to collect data about what is being thrown off of power lines and various other sources in the house to reach some conclusions. An issue is, the meter can ...
0
votes
1answer
128 views

Is this a correct addition to a pipe friction loss calculation?

I've been using this online calculator to work out the difference in pressure and flow between two ends of a pipe: Pipe Friction Calculation for Fluid Flow in a Pipe So far most of it makes sense, ...
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votes
2answers
3k views

static friction problem without mass

I am having trouble with a physics problem. The problem is as follows: A car is traveling at 54.0 mi/h on a horizontal highway. A) If the coefficient of static friction between road and tires on a ...
0
votes
0answers
46 views

Why is Avogadro's constant not exactly the inverse of the atomic mass unit (kg)?

First, Avogadro's constant (in essence, but off in terms of decimal place) is the inverse of the atomic mass unit (kg). Why are the two constants off by 10^3? Look at the picture for a quick diagram ...
0
votes
2answers
50 views

What does J cm-1 stand?

For an optical component, I got following number as an optical damage threshold from the company, damage threshold = 10 Jcm-1,20ns, 20Hz It looks like 20ns is ...
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0answers
8 views

Having trouble with linearly varying potential values (semiconductor band modeling)

One way to model an electric field-induced potential along a 1D semiconductor is: $$\phi(z) = eE_\mathrm{field}z\quad [\mathrm{eV}]$$ I'm troubled with the values, however. A typical electric ...
0
votes
0answers
30 views

How to calculate apex angle of sun shining on the Earth

I'm trying to compare the brightness of various LEDs to the average brightness of natural daylight. LEDs are rated in terms of candelas whereas the Sun is measured in terms of lumens, so I need to ...
0
votes
0answers
32 views

Easy unit conversion in Kerr metric

I would like to use Kerr metric in Boyer-Lindquist coordinates in geometrized units with mass of the black hole normalized to $M=1$. I am embarrassed to admit, but I can't seem to figure out how to ...
0
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0answers
38 views

Does unit linear scale lead to linear scale of time?

I'm modeling movement of charged particles on computer using Coulomb's law and Newton's motion laws. As I try to simulate motion of small particles on small distances with small charges, I use my own ...
0
votes
2answers
129 views

How the standard units for length force and time are defined in US Customary Units as standard units are defined in SI?

I'm much confused about US customary units so I want to ask a lot more questions under single question.First how standard units ,in US customary Units,of force time and length are defined as second or ...
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votes
0answers
96 views

How do I convert pressure and flow from Imperial to metric units?

I'm not a physicist or have much experience in engineering. However, for a programming task, I need to change code that calculates "pressure, head, feet of fluid, gauge" into "meters of head, absolute"...
0
votes
1answer
73 views

Units in Plasma Physics

What are the units people use in plasma physics? I am having hard time converting an equation from an old paper to SI units. I saw temperature being defined in $eV$. I assume this is $eV/k_B$ with $...
0
votes
1answer
124 views

Speed to power conversion

Here it is stated that there is a cubic relationship between fan speed and power consumption (Pfan ∝ FanSpeed^3). I have the fan speed (m/s), but I need to convert it into power (W). How can I compute ...
0
votes
1answer
27 views

Recalculating lux from EV

I have to calculate amount of light from IR emmiter. The only equipement, that I can use is Sekonic Light Meter like this one: http://www.ebay.com/bhp/sekonic-l-358 The problem is that i need to have ...
0
votes
0answers
48 views

Heavyside Lorentz units and Gaussian units

What is the relation between Heavyside Lorentz units and Gaussian units? From this Wikipedia article, I noticed there are $4\pi$ difference between them, but my TA wants more. Is there other ...
0
votes
0answers
42 views

Conversion from Curies to current of alpha particles

Is the following conversion correct from microCuries to Amperes? $\mu Ci=(1$x$10^{-6}Ci)$ x $(\frac{3.7x 10^{10}Bq}{Ci})$ x $(\frac{2e}{\alpha})$ x $(\frac{C}{e})$ Becquerels are $\frac{decays}{s}$ ...
0
votes
1answer
79 views

Any suggestions for units conversion? [duplicate]

Possible Duplicate: Photometer: measured Irradiance L converted to photon rate I am conducting a experiment where stimulus output of $470\ nm$ is measured by a radiometer at $30\ \mu W\ cm^{-2}...
0
votes
1answer
2k views

Question Based On Units And Measurements Involving Lengths [duplicate]

The below is the sixth question of the very first chapter from halliday and resnicks fundamentals of physics text,which i'am not able to comprehend. Harward Bridge,which connects MIT with its ...
0
votes
2answers
60 views

Proper units for physical quantities when $\hbar$=$1$

How to deal with the units of quantities if $\hbar=\tfrac{h}{2\pi}=1$? For example, the energy $E=\hbar\omega$: If I have chosen $\hbar=1$, how do I use the units to properly differentiate between ...
-1
votes
4answers
394 views

How do I use the kinetic energy formula using mass as lbs and velocity as mph?

I understand that the formula for kinetic energy is: $(1/2)mv^2$, which is equal to 1 Joule or 1 N-m. If I want $m$ to be my weight (say 150lbs) and $v$ to be 40mph how do I apply it to this formula? ...
-1
votes
3answers
333 views

Help getting the distance an object has moved

What is a distance an object went through at the speed of 14hm/min for 6 hours? I am having problems with conversions. First, I tried passing 14hm/min to m/s. I did it alright. But now I am unsure. ...
-1
votes
2answers
88 views

cm^-1 and ns^-1 relationship

In my last Phys.SE question Emilio Pisanty mentioned this relationship $1 cm^{-1} = 10^n c^{-1} ns^{-1}$. I was wondering where this relationship came from. Does anybody know? Second of all, I am not ...
-1
votes
1answer
42 views

Is there a software to convert units for quantities and equations? [closed]

For example, Often I end up with a complicated equation that uses non-standard units. In these equations, Temperature is in eV and Magnetic field is in Gauss. I need to convert my equation to another ...
-1
votes
1answer
93 views

In the expresion $4\sin (\theta) \frac{d \theta}{d t}=\frac{dy}{dt}$ Which is the correct unit of $\theta$ ¿ radian or degrees? [closed]

If I change units of an angle for radians to degrees in the next expresion $$4\sin (\theta) \frac{d \theta}{d t}=\frac{dy}{dt}$$ the value of $$\frac{dy}{dt}$$ changes. For example at a rate of ...
-1
votes
1answer
850 views

Convert units from cal cm^-1 day^-1. to Wm-2

I am trying to calculate the energy budget of a water body and the last term I'm trying to calculate is the energy advected from the water body ($Q_v$). This equation is given by: $Q_v = V ( (T_1 - ...
-1
votes
1answer
71 views

Why is the first term of First Law of Black-Hole Thermodynamics in other unit than in joule? [closed]

http://en.wikipedia.org/wiki/Black_hole_thermodynamics#The_First_Law http://www.physics.umd.edu/grt/taj/776b/lectures.pdf (p.13) The 2 sources have various forms of the same law. I found both are ...
-2
votes
1answer
36 views

In this energy conservation problem, why are the answers different with different units? [closed]

Really basic question, but basically I'm given a change in height in centimeters (that's how I measured it). From that, I'm supposed to find the initial kinetic energy. $KE_i = PE_f$ After doing ...
-4
votes
3answers
16k views

What is the fundamental units for coulomb? [closed]

Everything I saw suggests coulomb has no fundamental units. So then how is Newton/Coulomb equivalent to Volt/meter?
-4
votes
2answers
86 views

Converting PSI to Velocity [closed]

The question I'm asking is pretty much: How do you convert PSI to Velocity? Everywhere I look it says You can't, but can you? And what would you need to know to ...
-4
votes
1answer
250 views

How to find Area given Diameter [closed]

I need to convert diamter to area. I have (1/2)'' diamter acting on a steel cable. I need to calculate the stress, which is: o- = Force/Area The Force we know to be: F = 1000 lbs (pounds). Perhaps, ...