What is parts: Definition and 838 Discussions

In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are parts-per-million (ppm, 10−6), parts-per-billion (ppb, 10−9), parts-per-trillion (ppt, 10−12) and parts-per-quadrillion (ppq, 10−15). This notation is not part of the International System of Units (SI) system and its meaning is ambiguous.

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  1. skibidi

    Kirchhoff's law: Find the current I3 through the Amp meter

    I separated the circuit into parts- upper and lower For the upper loop I wrote: -14-2I1-3.4I3-I2 = 0 For the lower loop I wrote 16-2.9I2+3.4I3-5.4I2 = 0 I solved for I1 and I2 separately and plugged it into the junction rule and solved for I3. I may have got it wrong because of the...
  2. vibhuav

    I Physical meaning of two independent, non-interacting parts

    I keep coming across this descriptor, "two (or three) independent, non-interacting parts," in many books on QM (for example, Penrose's Shadows of the Mind). It is usually followed by a mathematical description (for example, state vector |A>|B>). I can wrap my mind around the quantum paradox of...
  3. S

    Solving this definite integral using integration by parts

    Using integration by parts: $$I_n=\left. x(1+x^2)^{-n} \right|_0^1+\int_0^{1} 2nx^2(1+x^2)^{-(n+1)}dx$$ $$I_n=2^{-n} + 2n \int_0^{1} x^2(1+x^2)^{-(n+1)}dx$$ Then how to continue? Thanks
  4. K

    Degrees of freedom (question based on an interview I attended)

    I was asked by an interviewer the number of degrees of freedom (in both translation and rotational senses) this part has with respect to each axis. Indeed I can share what I think of here, but I want to start it fresh and correct. If you were the interviewee, what would have been your answer and...
  5. D

    Rate of cooling of aluminum parts after a glycol heat process

    I work for an aerospace supplier across different departments. I was recently shown how the production workers straighten aluminum parts after a glycol heat solutionizing process. The aluminum parts undergo a heat treatment for a few hours and are quenched in glycol. I can't get too in-depth...
  6. alan123hk

    B Decompose the E field into conservative and non-conservative parts

    Recently, I've seen several discussion threads here about splitting electric fields. I want to express my opinion. Of course, this is just a calculation method, not a basic physical concept, but it is also useful in some cases, at least not wrong. The following is an example of the out of a...
  7. L

    I Why Does Quantum Entanglement Seem Puzzling Compared to Everyday Correlations?

    Suppose someone throws coins and once they fall on heads or tails, she saws them along the middle on two parts: one pointing towards the ground and the other pointing from the ground. Then she sends those two parts into opposite directions so after some time they reach two distant planets, one...
  8. S

    Omission of parts of equations in solving oscillation questions

    Perhaps that's a very dumb question, but I'm having a hard time to understand why it's possible to omit parts of the equations in solving various problems involving oscillations. Here, for example, the complete equation for acceleration is not used (the part with cosine doesn't appear) and here...
  9. L

    Medical Derealization parts of brain? (schizophrenia)

    I have read people with schizophrenia and DID may experience thinking that the world has become less real. Are certain parts of the brain acting up that could be making reality seem less real?
  10. M

    I just have a couple questions about parts on an F-16

    Hello I am just curious about something. In the image above, the spike shaped thing at #1, and the long thing at #2, what are those and what are their purposes? Since I don't know what they're called I can't google them lol. My current guess is that #2 is a mount for missiles, and #1 has...
  11. A

    A Feynman parametrization integration by parts

    How can i move from this expression: $$\frac{4}{\pi^{4}} \int dk \frac{1}{k^2} \frac{1}{(1+i(k-k_{f}))^3} \frac{1}{(1+i(k-k_{i}))^3}$$ to this one: $$\frac{4}{\pi^{4}} \int dk \frac{1}{k^2} \frac{1}{(1+|k-k_{i}|^2)^2} \frac{1}{(1+|k-k_{f}|^2)^2}$$ using Feynman parametrization (Integration by...
  12. rstor

    I Keisler Elementary Calculus: computing standard parts of expressions

    In Keisler Elementary Calculus page 39, example 4 it shows how to compute the standard parts of the following expression: Example 4: If ##\epsilon## is infinitesimal but non zero, find the standard part of ##b=\frac {\epsilon} {5-\sqrt{25+ε}}## Before calculating the standard parts the...
  13. K

    I Wavefunction of a free particle has carrier and envelope parts

    If ##\psi(x, t)=\left(\frac{1}{2 \pi \alpha^{2}}\right)^{1 / 4} \frac{1}{\sqrt{\gamma}} e^{i p_{0}\left(x-p_{0} t / 2 m\right) / \hbar} e^{-\left(x-p_{0} t / m\right)^{2} / 4 \alpha^{2} \gamma}##where * ##\gamma=1+\frac{i t} {\tau}##( a complex number) * ##\tau=\frac{m h}{2...
  14. novinox

    Need help to identify the parts needed

    Hi, I am trying to build a tortilla pressing device. If possible could anyone let me know what are the parts i need to get and also the size/power of the pneumatic cylinder should be. Thank you.
  15. R

    B What parts of an EMW does a ferrite rod antenna respond to?

    Hi. Would it be true to say, that a ferrite rod antenna, operating at fairly low frequencies (say 1Mhz) for all intents and purposes, only responds (in terms of voltage output) to the magnetic field part of a "radio wave"? Thanks.
  16. S

    Condensed parts of Earth's atmosphere

    How much of Earth atmosphere consists of condensed phases? What is the breakdown of these condensed phases between those that condense in atmosphere (water) and those that do not (rock)? The total amount of water in Earth atmosphere is quoted as a 25 mm layer on average - total of about 13 000...
  17. R

    Cauchy Riemann complex function real and imaginary parts

    Hi, I have to find the real and imaginary parts and then using Cauchy Riemann calculate ##\frac{df}{dz}## First, ##\frac{df}{dz} = \frac{1}{(1+z)^2}## Then, ##f(z)= \frac{1}{1+z} = \frac{1}{1+ x +iy} => \frac{1+x}{(1+x)^2 +y^2} - \frac{-iy}{(1+x^2) + y^2}## thus, ##\frac{df}{dz} =...
  18. JD_PM

    Rewriting a given action via integration by parts

    I simply plugged \phi = \phi_0 (\eta) + \delta \phi (\eta, \vec x) into the given action to get \begin{align} S &= \int d^4 x \left[ \frac{a^2}{2}\left(\dot \phi^2 -(\nabla \phi)^2\right)-a^4V(\phi) \right] \nonumber \\ &= \int d^4 x \left[ \frac{a^2}{2}\left(\dot \phi_0^2 + (\delta...
  19. S

    Art Notation for drum parts when scores were hand written?

    In the days when scores were written by hand, how were parts for drums written? It's clear that ordinary notation is sufficient to indicate the duration of dumb beats - although writing each beat for a drum would be tedious. Was there some system of abbreviation? Did composers attempt to...
  20. greg_rack

    Why Does My Integration by Parts Result Differ?

    Hi guys, I've attempted to integrate this function by parts, which seemed to be the most appropriate method... but apparently, I'm getting something wrong since the result doesn't match the right one. Everything looks good to me, but there must be something silly missing :) My attempt:
  21. Mayhem

    B Why don't we account for the constant in integration by parts?

    As we all know, integration by parts can be defined as follows: $$\int u dv = uv - \int v du$$ And the usual strategy for solving problems of these types is to intelligently define ##u## and ##dv## such that the RHS integral can easily be evaluated. However, something that is never addressed is...
  22. N

    Separating a wave function into radial and azimuthal parts

    I know how to work through this problem but I have a question on the initial separation of the wave function. Assuming ##\psi(\rho, \phi) = R(\rho)\Phi(\phi)## then for the azimuthal part of the wavefunction we have ##\Phi(\phi)=B\left(\frac \rho\Delta cos\phi+sin\phi\right)##, but this function...
  23. Tony Hau

    I How to interpret integration by parts

    So I am confused about a proof in which the formula for expected value of velocity, ##\frac{d\langle x \rangle}{dt} ##, is derived. Firstly, because the expected value of the position of wave function is $$\langle x \rangle =\int_{-\infty}^{+\infty} x|\Psi(x,t)|^2 dx$$Therefore...
  24. N

    Integration by parts on ##S^3## in Coleman's textbook

    I'm reading Coleman's "Aspects of symmetry" chap 7. On the topic of the SU(2) winding number on ##S^3##on page 288, three parameters on ##S^3## are defined ##\theta_1,\theta_2,\theta_3##. Afterwards, it defines the winding number and to show it's invariant under continuous deformation of gauge...
  25. D

    Automotive Diesel engine parts for post-treatment of diesel engine gas exhaust

    Hi folks, Any idea about what is it? I am required to find parts like these items which are made of stainless steel 304 and used on the post-treatment of diesel engine gas.
  26. Har2803

    How Do You Calculate Height Without Acceleration in Physics Problems?

    For parts (d) and (e) I can't figure out the required steps to get the height due to the fact that I don't have the acceleration. I may have done a miscalculation for the former questions as well. I also feel (e) requires the value of a. Hope someone can help me out. Been going at this question...
  27. JD_PM

    I Assuming boundary conditions when integrating by parts

    Let's present two examples $$-\frac 1 2 \int d^3x'\big (-i \phi(x', t)\nabla^2\delta^3(x-x') \big )$$ Explicit evaluation of this integral yields $$-\frac 1 2 \int d^3x'\big (-i \phi( \vec x', t)\nabla'^2\delta^3(\vec x-\vec x') \big ) =\frac{i}{2}\phi(\vec x', t) \nabla' \delta^3(\vec...
  28. T

    A Is physical reality more than the sum of its parts?

    There is a paper here: https://www.mdpi.com/1099-4300/19/5/188 And a lengthy article here: https://www.quantamagazine.org/a-theory-of-reality-as-more-than-the-sum-of-its-parts-20170601/ The general argument concerns causal emergence and whether all causal agency arises directly from the micro...
  29. T

    Has Anyone Used Xometry to Make Parts?

    Looking to get parts made and heard about Xometry. Has anyone here used them for CNC or 3D Printing?
  30. benorin

    I How do I separate the real and imaginary parts of an infinite product?

    Suppose you have a complex-valued function of a complex variable (namely, ##z=x+iy, \, \, x,y\in \mathbb{R}##) defined as the assumed convergent infinite product $$F(z)=\prod_{k=1}^{\infty}f_{k}(z)$$ Further suppose ##F(x+iy)=u(x,y)+i v(x,y)##, where u and v are real-valued functions. How to...
  31. N

    Shrinkage & Expansion of plastic parts

    Hi, I'm currently doing a shrinkage study upon this plastic part. I hv been observing how much can the part able to shrink over the time after molding, and now hv been on the 5th month observation. However, on the 5th month, the part starting to expand, compared with the data from the 4th...
  32. LCSphysicist

    I Integrate 1/(x*lnx): Integration by Parts

    can integrate 1/(x*lnx) by parts??
  33. Frigus

    On what basis are parts of the brain classified?

    On the basis of what brain is classified,like we say on the basis of function the neurons are of 3 types.
  34. K

    Calculate the current in all parts of this electric circuit

    In the circuit below, the output is 23 W across the resistor with the resistance 6 Ohm. Calculate the amount of current in all parts of the circuit as well as the polarity and EMF ε of the unknown battery. Circuit: My attempt: I get 6 unknowns with 5 equations. I don't know how to find the...
  35. Stephenk53

    Electronics Sites/companies used for electric parts

    Hello, I am building a battery pack to charge my laptop cooling pad and I am looking at batteries for it. I decided on LiPo because it is thin and thus should fit better on the cooling pad. I do not need help with the design since I am planning on using pre-made parts (although if you are...
  36. kunalvanjare

    Single-Step Flocculation for reclaiming Parts Washer wastewater?

    Hello, I am interested in knowing if a single-step wastewater clarifier/reclaimer can be made for used Parts Washer effluent. References can be found here :- 1. https://www.stingraypartswasher.com/stingray-mart-eq-1-wastewater-processing-system.html 2...
  37. T

    MHB The smallest circle that two parts of a semi-circle can fit into?

    So, true story: I made a large circular tortilla. Ate half of it. Then decided to put the rest into the fridge on a smaller plate.I raised the knife to cut the remaining semi-circle in two, and then went : "Hmmmmmmmm...". Anyway, it's in the fridge now with an approximate solution, but I'm...
  38. PainterGuy

    B The observable and non-observable parts of the Universe

    Hi, I'm only trying to understand the basic concept. Did the big bang give rise to both observable and non-observable universe? I have been through quite a few source and it seems like that the big bang was the cause of only observable universe and not of unobservable universe. Below I have...
  39. Like Tony Stark

    Body connected to two parts of a rope on an inclined plane

    The thing is that my professor said that if the velocity of ##A## is ##400 cm/s##, the velocity of ##B## is ##200 cm/s## because "##B## is connected to two parts of the rope and ##A## is conected just to one part", and he also said that that ##200 cm/s## is the velocity of ##B## with respect to...
  40. ohwilleke

    I How big are the non-mass parts of the stress-energy tensor?

    In Newtonian gravity, non-rest mass contributions to gravitational effects are ignored and for many purposes (e.g. low precision solar system astronomy, N-body approximations of galaxy or galaxy cluster dynamics), the other contributions that enter Einstein's field equations through the...
  41. brotherbobby

    Several parts of a system and its CM

    I have known and used this theorem for a long time solving problems ("Calculate the CM of the some given shape"). I took the theorem to be "obvious" and didn't know it could be proved (and that indeed it was a theorem at all). I can make no attempt at the proof. Any help would be welcome.
  42. PainterGuy

    B Decomposition of a function into even and odd parts

    Hi, I understand how any function could be decomposed into even and odd parts assuming the function isn't a purely even or odd to start with. It's just like saying that any vector in x-y plane could be decomposed into its x- and y-component assuming it doesn't lie parallel to x- or y-axis...
  43. mesa

    What are the most important parts of the job for a reactor operator?

    Hey guys, what would you say are the most important aspects of the job of being a nuclear reactor operator?
  44. S

    What machinery can these parts be used in?

    Found some old parts and was wondering if they look use able and what they could be used in. Apologies if I go against any of the forum policies.
  45. I

    MHB How to divide a circumference into equal parts, WITHOUT COMPASS?

    Hi guys I have the length of a circumference, how do you divide it into equal parts given a certain amount of parts? For example, I want to divide a circumference into 78 equal parts, and the circumference diameter is 1 meter! Whats the length of each part? And how do you calculate it? (no...
  46. M

    MHB A wheel of fortune is divided into 10 parts, one of them brings the jackpot.

    Hey! :o A wheel of fortune is divided into $10$ equal sized parts, of which one of them brings the jackpot. A player wants to investigate the regularity of the wheel of fortune. He turns the wheel 20 times. Calculate the probability that he will get at least one main prize if it is a...
  47. looseleaf

    A Understanding Integration by Parts in Quantum Field Theory

    Hello, I'm just starting Zee's QFT in a Nutshell, I'm a bit confused about what he means by "integate by parts under the d4x". Can someone explain what he means by this? I understand how to obtain the Klein-Gordon equation from the free particle Lagrangian density, but not sure why he invokes...
  48. C

    Are there organelle parts circulating blood?

    Hello, Once reading about renal function I think, I read that there are actually parts from organelles circulating in blood that have a specific name. They also function as messengers. But I cannot find anything about it now, any idea?
  49. SpaceIsCool

    Transverse velocity and real/imaginary parts?

    Homework Statement The transverse velocity of the particle in Sections 2.5 and 2.7 is contained in (2.77), since By taking the real and imaginary parts, find expressions for v_x and v_y separately. Based on these expressions describe the time dependence of the transverse velocity. Homework...