Calculations Definition and 983 Threads

Dear all, periodic DFT codes (e.g. VASP) effectively simulate an infinite crystal due to the periodic boundary conditions. However, the energy value that one obtaines at the end of a simulation if finite. Frankly, I'm quite confused right now. Is the energy to be understood 'per unit cell'...

Homework Statement A total charge of 50 Ah is stored in a 12 V battery of a car. Each of the bulbs of the four parking lights is labelled 3,6 W / 12 V. Homework Equations a) Find the current from the battery when only the parking lights are switched on. b) What is the resistance of one bulb...

Homework Statement I'm on the very last section of a question for the design of a simple gear train. I've managed to design the gear train with all criteria fulfilled and I am confident that it is correct. I just need clarification that my calculations thus far are correct and also a fresh...

I am interested in mass flow rate in conveyor screw transportation http://www.colormaxsystems.com/wp-content/uploads/2013/11/5-screws-300x222.jpg any recommended book,engineering guides ?

Effects of a 150,000 kilogram object launched at Earth, just below the speed of light: 99.99999999999999 percent 'c' speed.The object weighing 150,000 kilograms gets a relativistic mass increase of 183,648,173,214,437,391 kilograms, therefore getting a relativistic energy of...

I am not sure where to put this question in biology or maths forum.But i finally decided to ask here.Somatic cells have two "copies" of each of chromosomes, one inherited from each parent. Each sperm cell, on the other hand, only gets one "copy" of each chromosome (either the one from your mom...

Hey guys First real thread besides my introductory thread. I'm a Danish student in what is somewhat equivalent to my junior/senior year in the american school system. That was a small attempt at school system conversion. I'm writing a project about the black hole Sgr. A* in the centre of our...

And how do you find the drag force?

Homework Statement A capacitor of capacitance 12*10^6 is fully charged from a 20V d.c. supply. i Calculate the charge stored by the capacitor. ii calculate the energy delivered by the dc supply iii calculate the energy stored in the capacitor. iv account for the difference between your...

I'm coming out with a new logic in about a year which hopefully will be the first step towards solving the common sense problem in AI as well as making metaphysics more scientific. I'm afraid people will be unwilling to the hard work of performing the calculations I recommend.

Hello! I am in the beginning stages of designing a system that would drive a generator using gravity - similar to an old grandfather clock. I have a couple of questions about my assumptions/design that I am stuck on: - I found a motor which is rated 6v-12v DC, 188 RPM @ 12V with no load, and a...

Homework Statement A mass m of water cools down from 50degc to 10degc (the temperature of the surrounding environment). Calculate the entropy increase of the system (the water). The water has specific heat capacity c. Homework Equations dS=dQrev/T S is entropy, Q is heat added to the system, T...

Homework Statement The op am in the circuit shown is ideal. Calculate the following. a) Ia b) Va c) Vo d) Io Homework Equations I have found three equations one at Vn, Va, and Vo. The Attempt at a Solution The attempt solution is on the attachment. I currently have three equations with four...

I can’t find yield data for the concurrent creation and decay of fission products in an operating reactor. All the references I can find on the net are for the decay of a fixed lump. In an operating reactor the lump is (for a while) growing at the same time it is decaying. So, I started my...

Hi I am planning to make a DIY heat exchanger. It will be an air-to-air counterflow heatexchanger with equal air flow. I made a small test heat exchanger so I would be able to estimate the required size of the heat exchanger. I did a small experiment with the small exchanger. The outcome is that...

Ok, I have used every calculator I can find, typed it in several different ways for the past three hours and at this point I am giving up and asking for help. 1. Homework Statement A rock is thrown from the edge of a 14 meter high cliff with a velocity of total magnitude of 7m/s. Find the...

I need help calculating the size of the wood members I need in my truss. I understand the basics; I first need to calculate the load, then the stress on each member, then pick a wooden member which has that stress with a safety factor of let's say 2.0. The reason why I want to perform the...

Homework Statement Initial velocity=15m/s slows down to 10m/s in 4.0s. Acceleration= -1.2m/s^2 How far does the car travel in 4.0s If the car were to slow down at the same rate how much additional distance would it travel before coming to a complete stop Homework Equations A=d/t D=(1/2)at^2...

Hi there. I have come to this forum to try and find someone able of helping me with some (im sure) basic Physics. I'm trying to work out the Physics behind the Prosthetic carbon fibre legs that Oscar Pistorius uses, a diagram would be incredible! I want to know what calculations would be...

Homework Statement Calculate the individual currents in I2 and I3 (See diagram). I basically need to know how I calculate the current at any point in that circuit and that would help me. Homework Equations V=IR Rseries=R1+R2... 1/Rparallel=1/R1+1/R2 The Attempt at a Solution I honestly have no...

Homework Statement Hello everyone, I have completed a lab and I’m working on my report. I’m not sure if my work is correct but I would most definitely appreciate it if anyone could check it for me? I’m particularly having trouble finishing question #3. It’s worth a lot of my grade so I want...

Now, I had a collision approximately two weeks or so ago, however, I was the one blamed for the collision due to a "witness" but I need some help with the correct calculation I need. You see, her car weighed 2602 pounds, where as my car weighed 3359 pounds, but she hit me hard enough on the...

Please help. I am Trying to calculate the time taken to freeze a 16" carbon steel pipe that is full of water with no flow. The water is at 20 oC and am using Liquid nitrogen feed into an insulated pipe freezing jacket surrounding the pipe to freeze it. If anyone can help with the calculations...

Could someone explain to me the intuition behind RMS values? I understand how you calculate them; you take the average of the squares and square root them. I am just wondering why. For example when it comes to voltage, how did someone just think up of this magical way to compute an effective...

Hi all, I have been asked to contribute material for a presentation at my daughters school. The subject is alternative energy via solar methods and several other parents have already selected the obvious platforms (photovoltaics, CSP, etc.) and I thought solar updraft towers would be kind of...

The aim is partly pedagogical. I want to assemble some examples illustrating how the google calculator can play a role in learning cosmology and related. Suppose you don't remember the Schw. radius of the earth. Paste in "2G*mass of earth/c^2" press return, and you get 0.887 cm...

Recently I've been researching the pressurization of water through the releasing of the waters of hydration in hydrates. The goal is to create a volume difference inside a container of fixed volume, basically the volume of the contents should be greater than the volume of the container in order...

Okay, I created this topic because the other one seem to get no responses?! I found this paper that was useful to me : http://people.bath.ac.uk/enscjb/airtex.pdf It mentions the figure 2.0 - 2.6 L/min/kW. Is this kW, the bhp? Question 1:For a Nissan Maxima (3.5 L engine), could I take this...

I need a formula for deriving the required material thickness for an acrylic panel. The project will involve an acrylic window for a large aquarium. I have included a dimensional rendering. The maximum design stress must be maintained at or below 800PSI. The maximum water pressure...

Hi all, Newbie here. Forgive if I'm starting this thread in the wrong place! Started college physics this semester and although the physics is not the most challenging, I'm running into lots of trouble with the sig figs! First of all, when doing long calculations, where do you round the sig...

I have been interested in finding out more about this topic but I can't seem to find any articles/periodicals that don't assume you to already have 20 years experience with under frequency load shedding in transmission engineering. My questions are: 1.) How is it that you determine the amount...

Hi all I am very much a layman when it comes to Thermal Hydraulics and this may be a naive questions but here it goes... On the job, i use various codes to examine two phase flow in the core loop. Despite being vetted and validated numerous times over the course of many years (TRAC, RELAP...

Hi, thanks for stopping by :) This is for a big assignment (Yr 12). I asked my physics teacher this, but she couldn't give me a definite answer, and neither could my music teacher who previously studied physics, and then he messaged an engineer he knew, who hasn't replied yet... ~ Given...

Ok so the equation for the probability that a fast neutron will not leek out of a non infinite mass is Pfnl= exp(-(Bg)^2 Tth) so Bg is the geometric buckling and for a sphere that value is (pie/r)^2. My question is what is exp? And what is Tth / how do I get the value of it?

Hi guys, first time posting here, but I have a question that I have been thinking about for quite a while, and I hope someone can help out with it. Assume a line of charge (with overall charge of +Q and of length L) that is lying on the x-axis. You want to calculate the electric field strength...

Hi, My question is: Whats the whole point of solving the Boltzmann equation for relic density of dark matter? I mean, we already know the current density of dark matter in the Universe so that end is fixed by experiment. If we have a model of dark matter evolution then it has to comply to the...

Can anyone help me on how to save functions on a ti 36x pro for future calculations? I am doing a lot of plug and chug calculus and physics problems that would save me time if I knew how to save the functions and real them later, by changing what x is. Ie. Newtons method to finding roots...

I was so happy with the assistance provide here by NascentOxygen! Great contributor! I have another question: Homework Statement A 20V battery is connected to an inductor with 1000μH that has 1000 turns with a cross section area of 1cm^2 is connected for 0.3 Sec during where 20J energy are...

Hello, I'm new to this forum. I hope I am submitting this to the right thread. Just started physics and I am looking to get a little assistance Homework Statement A single loop carries 100mA and has an inductance of 100μH Homework Equations For air cored L = μ0 * (N^2*A/length) L = Nø/i...

Homework Statement I am currently working as an intern in a research institute (I'm a 3rd yr undergrad) and my supervisor has asked me to create a simulation from a particular model - please see linked <http://journals.aps.org/prb/abstract/10.1103/PhysRevB.69.045202> or attached paper. I...

I am building a shock damper for various weights which will be added at Mass D below. What I need to calculate is by how much would I need to turn my adjusters thus changing the angle of the spring, which in this case is 14.9 Kg rated, to allow for different weights to remain at a level...

I am attempting to complete a basic question involving molecular separation from Alonso & Finn "Fundamental University Physics" Second Edition, Chapter 2, Question 9. The Problem states "Using the data in table 2-1 and A-1, estimate the average separation in molecules of hydrogen at STP (gas)...

I'm reading a journal article that implies the following but I can't see how it is done. I'll give 100 DogeCoin (or equivalent) to whomever can explain this in full. Given that V(A|B) = s V(A) = r*s + w B = A + C and A & C are independent so V(B) = V(A) + V(C) & V(C) = V(B) - V(A) Then how...

Hi, I'm designing a gadget whereby I'm spinning a plastic propeller attached to a shaft which is attached to a 6V DC motor. I'm required to do a basic energy analysis of the set-up. The kinetic energy of the propeller is 0.5*I*w^2 (w=omega=angular velocity). Due to friction (air etc) then...

Homework Statement I have a radiator through which water is passed at 90 degrees Celsius, the air speed as it passes through the radiator is 4ms-1. Water temperature difference between inlet and outlet of radiator is 28.33 K. Temperature difference between air before and after passing through...

Hi! I'v been looking into this for way too long and have come to that point where nothing makes sense, hoping you guys could help me out! :smile: Basically i have been given a net head of 20m and need to provide a micro hydro turbine with 5kW of power for over one minute. What i want to...

Homework Statement Hello, I'm looking for some help on how to perform some lab calculations. We recently did a lab on the Preparation of Geometric Isomers. We were preparing the Cis and Trans isomers of butenedioic acid, i.e Fumaric and Maleic Acid. The Maleic acid was done by reacting...

Hi, Please tell me damper calculation.ie.how to calculate damping force??

The purpose of the lab was to measure, and also calculate, the induced current in a disconnected coil, due to a second coil connected to a power supply. Involved magnetic fields and electric fields (I think. For the purposes of this lab, the magnetic permittivity is 1.26*10-6, the number...

[b]1. I need to know the stress σ in the "y" direction. [b]2. I will use σ=P/A equation. [b]3. First (-2*10^6)N*0.4m=-0.8*10^6N Then σ=P/A=(-0.8*10^6N)/(0.4m*0.02m)=-100*10^6Pa. Is this corrects?