Units Definition and 975 Threads

Homework Statement Find 2 unit vectors u1, u2, lying in the plane, x-y+z=0, which are not parallel to each other. The Attempt at a Solution I've tried taking the unit vector of the normal vector <1,-1,1> which is <1/rad(3),-1/rad(3),1/rad(3)>, but my teacher has told me it is not in...

Homework Statement Prove that (a b c d) is a unit in the ring M(R) if and only if ad-bc !=0. In this case, verify that its inverse is (d/t -b/t -c/t a/t) where t= ad-bc. Homework Equations An element a in a ring R with identity is called...

Waves: String Physics?? Correct my units.. Homework Statement The velocity of a wave on a string depends on how hard the string is stretched and on the mass per unit length of the string. If T is the force exerted on the string and Mu is the mass/unit length, then velocity v is...

There seem to plenty of threads dealing with questions on topics such as "brightness" and how the human eye perceives objects under certain circumstances, so I've written up a mini-tutorial on how physicists quantify these concepts. 1. Radiometry and Photometry Radiometry is the measurement of...

Homework Statement Reading about the raditation dominated era I saw that the radiation energy density today was given by: \rho_r = \frac{\pi^2}{30} g_* T^4 = 8.09 * 10^{-34} g/cm^3 where g_*=3.36 is the degree of freedom of the radiation (equivalent) and T=2.75 K is the CBR...

My answer should obviously be in Newtons, but I'm getting Netwon meters. An aquarium, 2 m long, 1 m wide, and 1 m deep is full of water. Find the work needed to pump half the water out of the aquarium. (The density of water is 1000 kg/m3.) In a similar example in the book, they do the...

Homework Statement See Attachment Homework Equations The Attempt at a Solution Im just trying to figure out all of the forces, I am kinda confused about the whole T_{BDC} Do i just make these two separate tensions...and then add them together or something? Can someone explain...

Homework Statement If the ozone concentration in a particular sample of air were 25 dobson units, what sould this concentration be in: a)ppm b) %(v/v)Homework Equations 1 dob = 2.69*10^20 ozone molecules / m^2 http://en.wikipedia.org/wiki/OzoneThe Attempt at a Solution The question is asking...

I just got my blood test back and the numbers have some units I don't recognize, such as E9 and E12. The printer seems to not be able to handle very sophisticated formatting, for example: - one unit is listed as "UMOL/L" for Creatinine. I suspect that this is meant to be \mumols. -...

Up until my third year EM course we have used SI and MKS units in EM. In fact every textbook i have used for EM (griffiths,wangsness) also use those units. My current prof wants up to learn CGS units. While they do appear much 'cleaner' (no epsilon0, mu0 for certain equations) what is their...

Hey! I have always learned that functions like logarithms, exponentials, trigonometrics etc. have to operatore on pure numbers and not numbers with units. For instance, you cannot write: Sin ( 5 kg*m/s^2 ) But in chemistry I often find formulas where logarithmes of numbers with units...

Okay, if we are looking at a typical extended number field Q(w), and it's corresponding ring of integers, we know that for any given element in this field, it is not necessary that all of it's conjugates are in the same field. A typical example being: Q(\theta), \theta=\root 3\of{3}, \theta...

I have a simple question. I understand the quantitative differences between cgs and SI units, but when will I be expected to use one over the other? For example, do physicists prefer one set of units? Thanks for the help.

Time-oriented geometrized units→Second and its derivates in terms of 7 SI base units I expressed second in terms of meter and kilogram. For doing this I used: For expressing second in meters: 1s¹ = c = 299792458 m For expressing second in kilograms: 1s¹ = c³/G =...

I'm editing a school textbook and have suddenly discovered at the 11th hour that there is a difference between the U.S. cup (236ml), the Canadian cup (227ml) and the British cup (284ml) as well as conflicting results (such as Wiki) that define them differently again - U.S.=250ml, Canadian=240ml...

When I check units in the terms in Bernoulli's equation, they do not match: Given: p1 + 1/2 (row) v1^2 = p2 + 1/2 (row) v2^2 On the left hand side of the equation, the first term, pressure must have units of force/unit area; say lb/ft^2. The units in the second term are the product...

What are the units of the electric field strength H? I know that H = NI/L for a solenoid and I'm wondering if there is any condensed unit or if it is just ampere turns per meter.

density is (mass / volume). But what is (mass / area)? For example, if I wanted to know the mass of how much water would fill a jar, it would be mass = (volume of jar * density of water) = cubic length * (mass / cubic length.) But imagine I knew how much a square meter of paint weighed...

Somewhere a month or two ago, there was a discussion about E=mc^2 and the question of what the c^2 represents. The answer was that c^2 was simply a conversion unit, to put it in more common units of kg, m and s. That, if the formula were considered in more natural distance units of light...

Hi Everyone, I think I posted this message to the wrong forum, so second try... I hope this is the right one? Could someone please explain to me how I know when to use SI units to solve a problem and how to enter these units into an equation - are there any rules of thumb? If I could get a...

How does one figure out the units of measure for the cosmological constant? In the Einstein Field Equation: \[Rab - \frac{1}{2}Rgab + \Lambda gab = 8\pi Tab\] Lambda is a constant but the units of measure for gab and Tab differ for each combination of indices. For example T00 is an...

Im following a British curriculum for high schools ( known as A levels ) . I am reading stuff from this forum and i come across differences in notation used by the British and the Americans ... plus differences in units ... why is this so ? why couldn't u guys settle on one universal system of...

Is there a simple method for finding all the units in a polynomial quotient ring over a finite field? For example: {F_2[x] \over x^7-1} I can see the easy ones like 1, and all power of x, but I wanted a general rule or method for finding all of them if it exists (besides testing each...

Quick question. If i pass into a trig function something like cos(3pi*15 seconds), do I drop the seconds from the resultant answer since it's not a valid unit of measure for theta?

hihi for example, I am doing a question involving the probability of the number of apples i eat in a day. i need to find the mean, mode, median, variance and standard deviation. do these values need to be in units of apples? or just like a numerical value such as 2.3 ? thanks

Can anyone help? I don't understand how to do this for example: how many cm cubed are in 1 metre cubed? I am really stuck, your help would be appreicated. Thanks in advance.

Question: An object is moving on land at a speed of 1020 km/h. This object goes from full speed to a complete stop in 1.4 seconds. In g units, what acceleration did the object 'experience' while stopping? My guess is I have to plug in -9.8 m/s into this equation, but I'm not sure how. Any...

I have just started the AS Physics course and we have been doing base units, base quanntities, derived units and drived quantities. This stuff completely baffles me, and cannot find a site which explains this stuff in bog standard english. Please could someone help me. Thanks, Ben

I have search my gigantic physics book everywhere for this but I can't seem to find it...does anyone know what it means Seee the problem is What constant acceleration, in SI units, must a car have to go from zero to 71.0 mph in 13.0 s? I solved that it was 2.44 m/s^2 but then it askes What...

I'm confused when it comes to converting units. Ok here's a problem, what is 70 µm in meters? kilometers? I know that one µ equals 10^-6 so does that mean 70 µm = 0.000070m? I did 70.0 and counted forward 6 decimal places to get my answer. But I don't think I did it right. How would I do...

Been many years since I took general and org chem and am currently reading general chem textbook as refresher. Came across defintion of amu (atomic mass unit). Text says that the mass of the carbon-12 atom is defined to be exactly 12 amu. However, a couple of pages over, I read that the mass of...

Nice free units converter http://www.kamlex.com/index.php?option=com_content&task=view&id=12&Itemid=28

If you inspect the QED lagrangian, you'll find that the electromagnetic vector potential must have the units of [1] energy. According to Peskin and Schroder's QFT text, the expansion of the electromagnetic field operator is...

I solved the problem, but I can't get the right unit for the answer. A Carnot engine whose low-temperature reservoir is at 16°C has an efficiency of 31%. By how much should the temperature of the high-temperature reservoir be increased to increase the efficiency to 70%? My numerical answer...

So Hi, how you transfer from MeV to Joules? Thx, Exam this Friday :)

Hello, as you see I'm trying to translate Henry's coeff. from mol kg-1 atm-1 to Pascals. Did anybody try it?? thanks, merely

Metric unit conversions - 100 square kilometers to square centimeters Wouldn't the answer be 10000000? English units to metric units - 200 cubic yards to cubic centimeters How would I solve that? And does anybody know how I would enter my answers in the correct Unit Multiplier...

I found the formula for the period of a pendulum: --- T = 2∏√( L / g) T: Time L: Length of Pendulum g: Gravitational Force --- However, I couldn't find information about the units! If somebody could provide me with information regarding this, it'd be greatly appreciated. Thanks :cool:

I've been reading a book called Physics Demystified. I'am currently on part 1 Classical physics, chapter 6 units and constants. I have some questions about some defftions and units: The meter: It says that the meter is defined by the distance of light travels through a perfect vacuum in...

Express in the simplest form the units resulting from the following. (1) [kg/m^2][m^2/sec], (2) [m^3/kg][kg^2/sec], (3) [m^5/sec^2] / [m^3/sec^3], (4) [(kg^2 x coul^2)/(sec^3)] / [(coul x kg)/(sec^2)]

So far, all i can think of is: mass, time, length & charge (maybe?). Temperature isn't even a fundamental unit, since it is a measure of kinetic energy of a particle (1/2*m*vrms^2=3/2*k*T, i think that's right...), am i missing any? If that's all of them, then that's pretty amazing to me.

now, this is a rather basic question, but, i can't seem to find the answer... so anyhow, i always thought that a gradient diddent need units and was just used to compare the change between two things, but i think i may be wrong. so, if you are plotting extension (m) over force (n) for a...

http://www.simetric.co.uk/ " Info on SI Units " SI Unit Descriptions " SI Derived Units " SI Prefixes (mega, giga) " Imperial/UK Units " Scientific Notation --(i.e. what is 1.00E+09) " Metric Forum " Feet to metres calculator " Metres to feet calculator " British Thermal Units...

A quick units question. Serway gives the R value (for insulation) in English system units as: \frac{ft^2 \, ^o F \, h}{BTU} What unit does "h" represent? Thanks! -Dan

What is time ? My maths is so rusty its almost non existant. I'm looking at the energy to mass equivalence formula and trying to work out an equivalent 'unit of time'. With my poor maths I get; e=mc^2e^(1/2)=m^(1/2)* c [In terms of units] e^(1/2)=m^(1/2)* (d/t)e^(1/2)*t=m^(1/2)* dt= d *...

Hi, maybe someone could answer this for me, or at least confirm my answer. (It's not homework.) What objects, in General Relativity, carry units? My thinking is that coordinates, x^i, on manifold patches have no units. And the parameter, t, for a path x^i(t) has no units. So velocities with...

I started reading Lectures on Electrical Engineering Vol I, Steinmetz. I thought I should be able to understand most of it, but I don't get the first page! It says that: 'The total number of lines of force issuing from a magnet pole is called its magnetic flux. The magnetic flux, phi, of a...

I am programming a module used to convert measurement units. This will be part of a system that supports complex numbers. I never use complex numbers in my field but of course engineers and physicists do so I thought I should ask a couple of questions first. Q1. Is there anything unusual about...

B = k / w ( Z x E) Check this equation by deriving the units for B w = omega Z = z hat

OK so my whining for help covers writing a paper about how things would be different if the speed of light was changed to 65 mph. Right after getting the assignment I started thinking about dilations and all that. Then, I remembered Planck's constant. Light would still have to have the same...