Calculations Definition and 983 Threads

Why do we multiply permittivity of vacuum with relative permittivity? What does this calculation mean?

so I was reviewing my textbook on calculating electric field when we can assume a continuous charge distribution and they said three useful tools are (1) making use of symmetry (2) expressing the charge dq in terms of charge density lambda (3) and checking the answer at the limit of large r...

I have not found a straightforward explanation on how to perform voltage drop calculations for cables used for instrumentations purposes. Suppose you have Current Transformer (CT) and Potential Transformer (PT) connections coming into a relay (IE SEL421). If we have a cable that runs from the...

Homework Statement https://i.imgur.com/U8muIJS.jpg[/B] Homework Equations Not aware of any equations required. The Attempt at a Solution For these questions I don't understand what I'm suppose to even. I have researched the terms prefix notation and Identifying calculations but after hours...

I have completed the questions in the attachment I just need someone to tell me if they are correct and I'm doing them right. Thanks.

Hello, I'm trying to analyze the following system to get some idea about the forces present. The red line is supposed to represent the belt wrapped around the two drums. There is an extra part to the belt, however. Tangentially from the drum, a part of the string is attached to an unmovable...

Hi All, Is there a list of thermodynamics equations regarding the chiller process from condenser, evaporator, compressor to the regulator. Say I have chiller load at 90%, what set of equations could I use to determine the supply temperature of chill water and condenser supply temperature to...

Apologies for the stupid questions but I have confused myself. I was separating out blood components in lab- column chromatography- and now we have to calculate Na+ content of each fraction collected (in μmoles) and the protein content of each fraction in mg. Each fraction was 1.5ml. The Na+...

So I was studying on transformer calculations and understand it all pretty well until coming across these questions that I don't really understand. There's about 6 of them but if someone could work out 2 for me so I can understand it and finish it off it would be much appreciated. Thanks...

Hi , this may been asked quite a bit times but I can't really find a solid answer for this. Do we have to include negative signs during calculations for vectors or scalars? I have been told by someone that for vector quantity calculations such as Force we do not include the negative sign or...

hello. I have a ejection mold (steel) which has a bridge like mount which locates the handling eye bolts outward around hydraulic cylinders. I need to make sure the bolts in the bridge will not shear due to the sideways load when the mold is lifted or flipped 90degrees. Here is the known...

Hello everyone, the problem I have to solve is as following. You're in space and you're moving with a constant speed. Now, you want to accelerate. For this you will be using Newton's third law. Xenon 1+ iones will be shot from the back of the spacecraft with high speeds, the avarage speed...

At current I am trying to redesign a steam generator as seen in the picture attached, the requirements for this are as follows: · The water contain must have a minimum capacity of 2.25 litres · The heat loss as boiling point shall not exceed 75W in ambient of -3 C +/- 1 C · The fan shall have...

I know that slope in 2D = $$\frac{\Delta{y}}{\Delta{x}}$$. But what about 3D slope? I mean for every line in 3D there are 3 2D slopes. Those are: $$\frac{\Delta{y}}{\Delta{x}}$$ $$\frac{\Delta{y}}{\Delta {z}}$$ and $$\frac{\Delta{z}}{\Delta{x}}$$ But how do you combine those 3 slopes to form...

I have seen some tidal turbines that have funnel ducts around them to improve efficiency. So how would one calculate water acceleration in a funnel? If you want figures: water velocity - 3 m/s funnel opening A (largest) - 8 meters funnel opening B (narrowest) - 5 meters Distance between A and...

Hi guys, Hopefully a fairly simple question. All beam formulas I've come across, whether in my own textbooks or Machinery's Handbook, have two sets of formulas for beams. One will be for "simply supported", where one end is pinned and the other end is a pin-roller. The other connection type is...

Hello, this is my first post. This question is related to my final thesis. I'm calculating the heat exchange area of a radiator through heat exchange equations: Q = U*A*LMTD I have as data Q, and LMTD (this one through trivial calculations) In order to calculate U, I need the coefficients...

Hi, I am having trouble understanding how the signs were obtained in the moment calculation. When I imagine the 600 N force acting on the moment arm, it moves CW which would give it a negative value. When I solve the problem I end up reviving Ay and Cy values that are swapped with the book.

Homework Statement A flywheel made of glass fibre has been developed by BP to store the kinetic energy of buses when they come to a bus stop. The maximum energy stored in the flywheel is equivalent to the energy lost by a 16,000 kg bus braking from 48 km when it comes to rest. The bulk of the...

Hello! So I've been looking at making a decent calculation of the AU from the 2012 transit. As you can see from the first picture (Taken with the South Pole at the top), this is the method I'm using from the following video: I use 2*(Pi)/Period of Earth to calculate the angular speed from...

Homework Statement Guys, consider the above image. Let the incline to be smooth. If I want to find NET WORK .. There are 2 formulas .. W = Fd and W = Change in Mecahnical Energy In First Formula Wnet = Wf + Wmg Wnet = Fd - mgsin37 * d In second Formula Wnet = Change in KE + Change in...

I've developed a sort of aversion to doing huge calculations most of the time (at home) I just want to plug it into the calculator and do it . This is affecting my exams, I tend to put off questions which have a lot of calculation to do and then ultimately do the calculation wrong (We're not...

In computational physics is very often to calculate largest Lyapunov exponent. If largest Lyapunov exponent ##LE## is positive there is chaos in the system, if it is negative or zero there is no chaos in the system. But what can we say about some certain value of ##LE##. For example...

Homework Statement A monochromatic, electromagnetic plane wave is traveling in a non-conducting, transparent medium. Its real electric field is described by: ##E=100 \ cos (7.62 \times 10^6 (x+y+z) \ - \ 2.98 \times 10^{15} t) \ \frac{1}{\sqrt{5}} (\hat{y} + 2 \hat{z}) \ V/m## (a) What would...

Hello! (Wave) The following Runge-Kutta method is given. $$ \begin{array}{c|ccccc} \tau_1 =0 & a_{11}=0 & a_{12} = 0\\ \tau_2 =\frac{5}{2} & a_{21} = \frac{5}{2} & a_{22} = 0\\ \hline & b_1 = \frac{4}{5} & b_2 = \frac{1}{5} & \ \end{array} $$ I have to determine the order of accuracy and...

I am having some trouble understanding what to use for the uncertainties in the Heisenberg principle. My chemistry book has two problems on this principle. One asks to find the minimum uncertainty in the position of a marble of mass 1.0g given that its speed is known within +- 1.0 mm/s. The...

This is the question I have been working through and I just want to know if I am on the right track. Any advice is appreciated. 10. The major industrial method for the preparation of elemental phosphorus is heating a mixture of phosphate rock, carbon, and sand in an electric furnace. The...

Hii, I am designing a rack and pinion steering system .I have strucked in finding 1)rack displacement,2)tie rod length. The inputs that I have inner and outter wheel lock angles,turning radius,lock to lock turns,steering ratio. If I get rack displacement,I can get steering arm...

Homework Statement So I'm looking at the radiation exposure risk regarding depleted uranium (U-238) and nuclear waste (4.20% U-235, 95.8% U-238). Yes I know these compositions are incorrect; they're close enough to exact for my purposes. The only information I have is the half lives of the...

We have a 90 deg C. rated PEX cable copper sized 1x185mmm2. This cable is to be used in 45 deg C environment (alone in air on a cable tray). We want to use it in intermittent operation where the cable will be loaded with 600 kW for 40 seconds, then nothing for 40 seconds. Then repeat. The...

Hi there, really trying to grasp these concepts for one of my engineering papers. This is basic stuff I realized now that I never really understood. If I've got two shafts, two wheels per shaft meaning four wheels in total, each wheel is 60 mm in diameter, and the power consumed by the system...

Hi there, I've forgotten how to solve these problems, eg: If I've got two shafts, two wheels per shaft meaning four wheels in total, each wheel is 60 mm in diameter, and the power consumed by the system in providing a constant horizontal velocity of 0.15 m/s is 200W, what is the torque in each...

Homework Statement This is a past exam question which I just for the life of me can't figure out. http://tinypic.com/r/2eq6ryo/8Homework Equations My guess is that the energy of the magnetisation is equal to the gravitational energy Relevant Equations: Ems = Mass * g * δ Where Mass = ρ *...

Hi there, In particle physics there is famous books as Peskin's book " To Quantum Field Theory (Frontiers in Physics) " to learn matrix element amplitude and cross section calculations, like ee -> mu mu. Are there similar references for supersymmetry to learn how to calculate the cross...

I'm reading T. Padmanabhans General Relativity. In section 7.6, he describes the gravitational collapse of a sphere of pressureless dust(So ## T_{\mu \nu}=\rho u_{\mu} u_{\nu} ##). I should say his argument is the same as Landau's, but reading Landau's didn't help too. At first, he assumes a...

I don't know how to get the oolarity from just the percentage See this question: Calculate the osmolarity of each solutions: 5% glucose solution .89% NaCl solution And 8% glucose solution i=1.9

Homework Statement The current in a certain circuit as measured by an ammeter is a continuous random variable X with the following probability density function: f(x) = 0.057x + 0.272 if 3 <= x <= 5. It is 0 otherwise. a) Verify that the total area under the density curve is 1. b) Obtain the...

Hi there, I'm planning to build a suspension bridge in my backyard and i'd like some help with sag and force calculations. The bridge will span 18m across a stream (anchor to anchor) in my backyard. I'll have 2 x strands of wire rope (1 at either side of the walkway) to span the gap. I've...

I have a rain barrel 20 feet below a deck. I want to pump water from the rain barrel up to a small container (2 gallons) once a day. I'm thinking it should take less than 15 minutes to fill. I've found a pump I like that has the following specs, but it may be too powerful, but it's cheap ($15)...

I am designing a flat plate heat exchanger for a project and I am not sure where to start with the hand calculations, specifically the LMTD and E-NTU methods, also how to work out the parameters which i will need to complete these methods such as area and number of plates. My deadline is soon...

Hello there guys I'm trying to find out which ball bearings I have to use for a new wheel hub I am designing. What I'm currently doing is a load analysis for the axis but I am confused on how would the forces that affect the wheel (normal, friction, lateral force when the car takes a turn...

Homework Statement Consider the specific case of a point above the axis of a circular ring of charge, how do the calculations follow to cancel the radial components? I understand the concept of the symmetry but don't understand how to express it in the expression without just removing the term...

Homework Statement Prepare a buffer solution of pH 3.746 from 25 mL of 0.244 M weak acid with pka 3.54 What volume, in mL, of 0.275 M NaOH would need to be added? I think that I have the answer but I am not sure, could you look over the working to check? Also, would you do this differently...

Homework Statement A vertical post is held in place by two cables as shown. Homework Equations SOH CAH TOA The Attempt at a Solution http://postimg.org/image/6rgssb1j5/ The answer in the textbook is 63 degrees. Is this an issue or did I do something terribly wrong?

I was studying 2nd law thermodynamics. In that context found the clausius's inequality saying closed integral of dQ/T <0 for irreversible process. And from the reversible process entropy was defined. And from that view they said that for irreversible process dS>dQ/T. Now when I saw some...

Hallo, Working on building a cloud chamber based on thermoelectric coolers rather than dry ice or other "consumable" cooling methods, and having some difficulty working out some of the numbers. Say I have a volume of air at room temperature, for arguments sake 1600cm³, and I want to cool this...

Homework Statement Calculate the total number of compex multiplications required for the calculation in (b) when FFTs are used to perform the Discrete Fourier Transforms and Inverse Discrete Fourier Transforms.[/B] There were two FFT multiplied together and one inverse FFT of that product to...

I want to make a leaf-vacuum using a leaf-blower. Does anyone know how I might calculate the pressures? Thanks!

Why isn't the ionization energy of an electron equal to it's energy level such that: E(electron)= -13.6(Z^2/n^2) = IP for that electron But instead it is equal to the energy difference in energy between the atom and its ionized cation: IP = E(A)-E(A+)

Hello, I'm working with a heat exchanger I'm trying to integrate into a cooling application. I've done some tests but want to have some clear understating of how the calculations are done or if I have missed something. Below is what I have so far. So it's a radiation with 2 pwm fans, they push...