Units Definition and 976 Threads

Show that the value of ##\int_0^1\sqrt(1-cosx)dx## is less than or equal to ##\sqrt2## ##1\ge cos x\ge-1## The problem is a worked one but I am just confused by a simple thing. We integrate the function f ##\int_0^1\sqrt(1-cosx)dx in the interval [0,1] but I don't understand that what stands...

In my textbook, it is talking about the Hall Effect on a flat conductor with width w carrying a current i in a uniform magnetic field perpendicular to the plane of the strip. It says that this will create a potential difference of V=E/w where E is the induces electric field from the electrons...

Hello everyone! I would like to ask a rather comprehensive question. I would appreciate it if you could help me with this. I have started reading a chemistry textbook recently and typically in the first chapter of any basic chemistry course, you come across, measurement, unit conversion, etc...

We are working on an IOT project in which we are trying to learn about different vibrations of using Wireless Vibration Sensor According to the manual, the wireless vibration sensor is giving the output while testing on CNC machine device 0.75, 0.71,0.69 whose SI units are in 'g'(which is...

Hi, I was wondering of those who might write papers in this field. What is the convention of units in plasma physics papers, and is this often all screwed around and you have to already understand it to understand it? I'll give you an example, because I am looking at this paper to understand...

Homework Statement If I am asked to give my answer in acceptable SI units and to 3 significant figures, how would I express my answer? Homework Equations Answer: 589883.4263 J The Attempt at a Solution My instinct would be to put this in KJ, but I don't know if that's an "acceptable SI...

Homework Statement Is N/m^2 a si unit I know Newton is and meters but togeather are there or is m^2 Homework Equations The Attempt at a Solution N/m^2 m^2

here's the question: a = b/e b = 1 kg m-1 e = 1 kg m-2 what is a? including units I assume it's to do with cancelling out the units when you divide but I really don't know what the answer is

I am not sure that this is the right place to post this question, so I will be happy to let any moderator move it. (I would be less happy to find out that the question has no place in PF, but I would accept it.) I have been asked to make a list of American manufacturers of plates for...

Homework Statement [/B] dp/dh = -.13*p h in kilometers I should convert it into meters2. The attempt at a solution I thought it would be enough to multiply -0.13 by 1000. :( dp/dh = -130*p but it is wrong.

Homework Statement I've an equation here: h = 3270 Pa / 1,0 g/cm^3 × 9,81 m/s^2 = 33 cm How did those units cancel out to make it cm? That's something I don't get. Homework Equations Given above. The Attempt at a Solution I've tried to cancel them out by looking at the same unit in the...

Why is the absorption coefficient (##\alpha##) of water is always given using the units ##\text{length}^{-1}##, while for other materials it is often given by ##\text{length}^{2}.\text{mass}^{-1}##? For instance, this paper uses ##cm^{-1}## for water and yet ##cm^2 / \mu g## for other...

Homework Statement A spherical balloon is being filled with air at a constant rate of ##2cm^3/sec##. How fast is the radius increasing when the radius is 3 cm? Homework EquationsThe Attempt at a Solution This is a problem given and spelled out in my text. However, it seems to be assuming that...

I am enrolled in a course related with physics, and we have a table of equivalencies of units to get the right units of frequencies. Stiffness Mass Frequency tonf/m ton.s^2/m rad/s kN/m ton rad/s N/m kg rad/s kgf/m...

This question is about the matching the unites in an equation. The equation for an electron mobility is given by m^2/V.S. However substituting the units in the equation, doesn't yield the unit of mobility [m^2/V.S]. I have done the simplification using mks units and didn't come up to m^2/V.S...

Homework Statement The following is the equation of ideal gas law, where p is pressure (Force/Area), V is volume, n is number of moles and T is temperature in Kelvin. What is the fundamental unit of R? pV = nRT A. kg^−1 · m^−2 · s^ 2 · K · mol B. kg^−1 · m^−4 · s ^2 · K · mol C. kg · m^4 · s...

How is it that when using "natural" units we drop the units themselves. I understand that you can arbitrarily change the magnitude of a parameter by choosing a new unit. For example Oliver R. Smoot is exactly 1 smoot tall. However, in natural units with [c]=[h/(2π)]=1 the "smoot" part is...

Quantumly speaking: Can speed be measured? If so, why? If not why? This is a serious question. Speed involves a distance unit and a time unit. For example .. "ft/sec" .. and it is illogical to divide seconds into feet. Having made this point can speed be quantumly measured and how do you...

Hi, I am currently studying aviation engine outputs and to make my study linear in comparative analysis with standard Automotive engines I need some expert help. Can anyone help me drive precise equations to convert: 1. Engine thrust in Kilo Newton into Horse Power and Watts 2. Engine thrust in...

This question is more for practicality than anything else, and I realize it may be partly subjective. At what temperatures can the 273 degree difference between Kelvin and Celsius scales be ignored? I'm thinking for examples regarding stars and very high temperatures. Surely once you get to 15...

Mentor note: Thread moved from a different forum section, so missing the homework template. I'm very confused about the attached questions on geometric buckling of a cylinder and a sphere. For this question I'm not given a value for the extrapolated distances (for R' and H') so I simply put the...

I am forever reading about how this or that country had an electrical power output of so many kW in a year (just kW, not kWh). And here is an article about the volume of California sea cliffs being described in "meters"...

Hello. This is the differential equation. $$ i \cdot \dfrac{R}{L} + \dfrac{di}{dt} = t $$ My solution path: Homogenous solution: $$ r + \dfrac{R}{L} = 0 \\ \\ r = -\dfrac{R}{L} \\ \\ i_{h}(t) = C_{0} e^{ -\dfrac{R}{L} t} \\ \\ $$ Particular solution: Try $$ y_{p} = at + b \\ \\ y_{p}...

When conducting numerical methods using 4th Order Runge-Kutta do the physical units have to be maintained? This never occurred to me until I was writing out all the steps in detail when showing someone I work with the method using a simple projectile motion with drag. It had 4th Order time...

The SI definition of a second was originally based on 1/86 400 of a day - but the Earth's rotation is a) unsteady and b) changing so it was changed to a defined number of cycles of an atomic clock. Was there a specific day for which the atomic clock was calibrated? Put another way, why were 9...

Homework Statement [/B] (1)A sphere of radius 0.500 m, temperature 27.0 C, and emissivity 0.850 is located in an environment of temperature 77.0 C. At what rate does the sphere (a) emit and (b) absorb thermal radiation? (c) What is the sphere’s net rate of energy exchange? (2)A cylindrical...

I need to convert mj/mm^2 to bar is there a way to do that ? I think we cannot ,bar is N/m^2 but we have j/m^2

Hi everybody. There has been a thread about this on physics forums, where the Fourier transform X(w) of x(t) volts (with time units in seconds) could be considered as volt second, or volt per Hz. So when we see tables of Fourier transform pairs, we might see Fourier transform plots associated...

I am an student in physics department and I will graduate very soon.In my past four year I have done a good work and get a nice gpa.But as I get more and more familiar with advanced content such as quantum field theory,I become very comfusing about what I learn in my high school. Because I...

Homework Statement My Teacher says that in the Schwarzschild metric he uses natural units, where he writes ##g_{rr}=1-2M/R## He says that for one neutron star ##R=5## corresponds to approx 13 KM. Homework Equations ##1l_p=1,616 \cdot 10^{-35}m## The Attempt at a Solution Unfortunately he does...

Recently, I tried to convert an energy density ##\frac{gram}{cm^3}## into ##(\frac{Volt}{cm})^2##. I faced some problems originating from the introduction of the superfluous unit ##Ampere## and its descendants in the system of units. On one hand, there are the transparent Gaussian units, in...

Hi, I need to convert a value of 12*10-16 m7 N-3 y-1 to the units of kPa-3 m2 s-1. Can anyone help me? where: m = meters, N = Newton, y = year, s = seconds. Thanks!

Homework Statement A problem will ask for an amount of substance in kilograms to be raised to a certain temperature and the specific heat be given in J/g*K. The amount of substance is not required to be converted to grams to match the units in the specific heat to get the correct amount of...

Dear members, The unit of stopping power is given as Mev/cm in many sources. It is easy to comprehend this unit.The mass stopping power, which is the total energy lost per path length by a charged particle, is defined as the division of MeV/cm to the density of investigated material, g/cm3, and...

As a physics undergrad, a set of natural units is nothing strange to me, we use them all the time. Having said this, I've never used Planck units. Does any area of research use them on a typical day in the office? There also seems to be this idea that I hear from time to time, perpetuated by...

Not sure if I'm posting in the wrong place.

Homework Statement During a short interval of time the speed v in m/s of an automobile is given by v = at^3 + bt^4 , where the time t is in seconds. The units of a and b are respectively: (a) m⋅s^2 ; m⋅s^4 (b) s^3/m; s^4/m (c) m/s^2 ; m/s^3 (d) m/s^3 ; m/s^4 (e) m/s^4 ; m/s^5 Homework...

Hello, I have question about transformer. How is Hermetically-sealed transformer cooled? I know that in air-breathing type we have conservator, breather, etc…for cooling. But, where the expansion oil goes in hermetically sealed? How it works?

Greg Bernhardt submitted a new PF Insights post Make Units Work for You Continue reading the Original PF Insights Post.

It is well known that most of the world use the SI system of units while the USA and a couple of other countries continue to use US Customary units (ft-lb-s = FPS or in-lb-s = IPS). The question of which is better is very much a matter of personal preference, but I'd like to avoid that issue...

Good evening, Does anybody know how to get the units of momentum flux? Momentum = kg m s−1 Flux = m−2 s−1 Somehow, I should end up with kg m-1 s-1 (kg m s−1) m−2 s−1 = kg m−1 s−1 However I end up with kg m-2 s-2 Is there anybody that knows what I'm doing wrong? :)

I am confused about the units used in Kepler's 3rd law. Is T supposed to be in years or days? Is R supposed to be in kilometers or meters? Is there ever an instance where one combination of units is preferable over another (for example, if you want to use the answers from Kepler's third law to...

It is a well known fact that, in electromagnetic units, strength of a shell and strength of current flowing through its boundary are same. See here. \begin{equation} \begin{matrix} \text{i.e.}\: i \text{(biot)} = \phi \text{(biot) } \end{matrix} \tag{1} \end{equation} (a) While converting to...

I am computing force between two magnetic poles each of one unit pole (in emu) and situated one centimeter apart. In electromagnetic units: ##F_{dyne}=\dfrac{p^2}{r_{cm}^2}=\dfrac{1^2}{1^2}=1 dyne## where ##p## is pole strength in emu In SI units: ##F_{N}=k_A \dfrac{P^2}{r_m^2}=10^{-7}...

Hi Everyone, I have to calculate the coefficients of the massive Higgs Lagrangian in natural units, ħ = c = 1. Do I assume firstly that, in these units the masses of the Higgs, W and Z are the usual, 125.09±0.21, 80.4, 91.2 respectively, and secondly that e has to have the value 2√(απ)...

Homework Statement [/B] When you drink cold water, your body must expend metabolic energy in order to maintain normal body temperature ( 37.0°C ) by warming up the water in your stomach. Could drinking ice water, then, substitute for exercise as a way to “burn calories?” Suppose you expend 430...

So the equation for angular acceleration on the AP physics sheet reads α = ΣT / I. I am required to prove that the units on each side are the same however I can't figure out how to get the rad/s^2 unit for angular acceleration into the same form as the right side which is N*m/ kgm^2 Any help...

Hi! My name is David. I'm a theoretical physicist from Stuttgart, Germany. Over the past months I have been developing an open source application called Insect, which I hope would be of interest to some of you. Insect is a high-precision scientific calculator that comes with full support for...

The topic has been discussed before at PF, in particular @haruspex's Insight Can angles be assigned a dimension? Nature has now published an editorial on the subject: SI units need reform to avoid confusion

Homework Statement Consider the slab shown in Fig. 18-18. Suppose that L 25.0 cm, A 90.0 cm2, and the material is copper. If TH 125 C, TC 10.0 C, and a steady state is reached, find the conduction rate through the slab. Homework Equations Pcond = Kc *A*(TH - TC)/L K = 401 W/m*k The Attempt at...