What is Per: Definition and 565 Discussions

PeR (Please Explain the Rhythm) is a Latvian pop and beatboxing band formed in 2007. The original line-up was Ralfs Eilands, Emīls Vegners, and Pēteris Upenieks. Vegners left the band in 2007 and was replaced by Edmunds Rasmanis. But when Upelnieks left the trio in 2011, he was not replaced, rendering the band a duo consisting of just Eilands and Rasmanis. After three failed attempts in earlier years to represent Latvia in the Eurovision Song Contest, PeR won the 2013 Dziesma contest and represented the country in the 2013 Contest with the song "Here We Go" and placed last in the second semi-final.

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  1. B

    Studying How to study multiple textbooks per math subject?

    Dear Physics Forum personnel, I am a college sophomore in US with double majors in mathematics and microbiology. I apologize for this sudden interruption but I wrote this email to seek your advice regarding to utilizing multiple textbooks per mathematical field. I always thought that...
  2. P

    Conversion pounds per square inch/pascals

    Heya guys, I am having a problem converting units like pascals and pounds per square inch. I do not understand, what "area" of measurement does a pascal cover as opposed to a "pound per square inch" obviously being in an inch, the pascal is per what area?For example when I try this to help me...
  3. P

    Pressure per square inch to pressure per square foot

    Heya guys, I and some colleges were discussing pounds per square and pounds per square foot and I wonder if you can help me with an answer, I would be grateful.So the question is, what is pounds per square inch relative to pounds per square foot? For example, if I had some flooring installed in...
  4. Dostetres

    Multiple BLDC per shaft for marine propulsion

    New to the forum, and can't find this info or examples on the web. I'm interested in the possibility of coupling multiple DC brushless motors to a single drive shaft for main propulsion on a 45-50', twin screw boat. Lots of sail boat examples are given, but my interest is in a power...
  5. A

    Calculating Per Unit Fault Impedance: Finding Errors in Given Relationships

    Homework Statement Given the relationships: Xpu = MVAbase / MVAfault Xpu = ( MVAbase / MVArated ) * ( X% / 100 ) MVAfault = sqrt(3) * V * Ifault Xohms = [ V / sqrt(3) ] * Ifault Homework Equations Show that: Xpu = [ MVAbase / V^2 ] * Xohms The Attempt at a Solution No matter how I...
  6. T

    Why is the speed of light 186,000 miles per second?

    Why is the speed of light 186,000 miles per second? Is that how fast the ether will allow it to travel? and if that is the case, if the edge of the universe; the edge to which the universe is speeding up, would the ether out there let light travel at higher or lower speeds? Which to me means...
  7. U

    Pressure drop per unit length of the pipe

    MODERATOR NOTE: THERE IS NO TEMPLATE BECAUSE THIS THREAD WAS ORIGINALLY MISPLACED IN A NON-HOMEWORK FORUM Viscous liquid (ρ = 1460 kg/m3, μ = 5.2×10−1Ns/m2) is pumped through a smooth pipe with a 0.1 m diameter, at a rate of 5×10−2m3/s. Using your Fanning friction factor versus Reynolds Number...
  8. M

    Charge per unit length for a charged ring

    Homework Statement If you have a ring of charge, is it valid to say lambda = Q/L, or is it lambda = dQ/dL? Homework EquationsThe Attempt at a Solution
  9. K

    Photons per second from lightbulb

    Homework Statement [/B] If 5 percent of the power of a 100 W bulb is radiated in the visible spectrum, how many visible photons are radiated per second? Homework Equations E=hf=hc/λ The Attempt at a Solution I know how to solve this, I just wanted to make sure. I will take 5 W or J/s as the...
  10. S

    How to convert Gallons Per Hour to PSI?

    Hey all I am a newbi and wondering how to do this conversion. When i see a water pump which is 1400G/hour at that rate what would be the psi? For example my garden hose is about 40psi and at that rate it would mean a curtain g/ph based on say a 15mm outlet radius. Im trying to figure out what...
  11. W

    Admissions Taking 3 courses per semester and graduate admission

    Hello forum, I will be an undergrad senior majoring in mathematics. Instead of taking the ordinary 5-course workload, I am thinking of doing 3 courses per semester and postpone graduation by an year. But I am wondering if by doing so my graduate application is going to be affected negatively. I...
  12. R

    Math in Moscow: Number of students per semester

    I'm looking into the Math in Moscow and have a very simple question which I can't seem to find answered online: Roughly how many students participate in the Math in Moscow program in a given semester?
  13. C

    Power system analysis, per unit system help

    Homework Statement https://dl.dropboxusercontent.com/u/88040310/powerhw3.png 1. Draw the reactance diagram. 2. Calculate the per unit impedances 3. If bms #1 is operating at 30 kV, find the current Assume base of 100 MVA, 300 kV on the generator side. Homework Equations P = VI s = p +jq...
  14. P

    Sound Waves: Energy per second

    Homework Statement Standing 20m away from a tower generating 2500W of power how much energy/s hits each of your eardrums? Surface area of eardrum=55mm^2 Assume that the speaker generates sound uniformly in a forward hemisphere. Homework Equations I=P/(4πr^2) r=20m P=2500W The Attempt at a...
  15. G

    Average percent growth per year

    Homework Statement If a stock has increased 400% over the last 6 years, then how much does it grow on average per year. Homework Equations 400 = 100(1+r/6)^6 The Attempt at a Solution Divide both sides by 100 4 = (1+(r/6)^6 Take the sixth root of each side. 1.26 = 1 + (r/6) Subtract...
  16. H

    MHB Help Solve This Financial Puzzle: Dropping Rebates Per Case

    Hi, I'm trying to prove something that I think is simple but am really struggling so would greatly appreciate any help! Over 2 weeks I receive rebates, the value of the rebate can vary both due to the rebate on each case and also the number of cases ordered. Between week 25 and week 26 my...
  17. supak111

    Laser to ionize air to run current, laser power per foot?

    Hey guys I know that a laser can ionize air so that you could run current through air. I was wondering if anyone could tell me just how powerful (watts) the laser would have to be If I wanted to connect 2 point that are about 100 feet apart? 2 points have very low current but do have high...
  18. H

    Thermal energy intensity per unit volume

    I am trying to figure out what the total thermal energy emitted by completely transparent matter. It seems Planck's law can't do this because the thickness or geometry of the mass is not given, only it's surface area. The spectral radiance of a black body is given by Planck's law...
  19. P

    Newtons to Newton meters per second

    Homework Statement Ok so 1000(5.556 m/s – 0 m/s)/0.055 = 101018 Newton’s which is a unit of force. We know the force was applied for 1 foot of travel (.3048meters) Homework Equations So the incorrect conversion would be to multiply by .3048 to get 30790 Newton meters per second. I am missing...
  20. D

    Energy of reaction: per moles of what?

    Disclaimer: I've never had a chemistry class in my life. I'm reading a journal article that states the following: S2O32- + 2O2 + H2O → 2SO42- + 2H+ has the standard Gibbs energy of −766 kJ/mol at 25ºC. So, this is energy produced per moles of what?! Reactant? Product? If so, which reactant or...
  21. R

    Engineering Engineering & Physics Degrees: Salary Overview

    Hello, I'm currently in college and getting a bachelors degree in physics and engineering, I also might get a bachelors in math too. I was wondering how much money I would start off getting with those degrees together? I've seen how much engineers get and physicist but what if you have both? Thanks
  22. S

    Number of bits per pulse width in buffers and delay lines (optical)

    Hi I was working on delay-lines and I wanted to know if a pulse is delayed by 10 pulse lengths through a delay-lines than what is the corresponding storage bit for that delay line. Thanks
  23. C

    Does CNS in spine have single fiber per inervated muscle?

    if I can move specific muscle in my toe via brain command, does this mean that in spinal cord there is a specific fiber that extends from brain to that toe? And let's say if in a lab rat we cut that single CNS fiber, the muscle affected will stop working without any other consequences to the...
  24. B

    Why is radiance defined per projected area normal to the beam direction?

    Radiance is defined as radiant flux per solid angle per projected area normal to the beam direction: ##L = \frac{d^2 \Phi}{d \vec\omega \cdot d A_\perp}## where ##A_\perp = A \cos \theta## and ##\theta## is the angle between the beam direction ##\vec\omega## and the surface normal. I kind of...
  25. B

    Calculating Steam Production in Fire Tube Boiler | 180ºC Dry Saturated Steam

    Homework Statement Dry saturated steam at a temperature of 180ºC is to be produced in a fire tube boiler from cooling of 50000 kg/h of flue gases from a pressurised combustion process. The gases enter the tubes of the boiler at 1500ºC and leave at 100ºC. The feed water is externally preheated...
  26. G

    Can you do more than 40 hours of calculation per week?

    I keep track of how much time I spend doing intellectual labor. It works out to 60% of my free time and 49 hours per week. I also separate my labor into two categories: hard and easy. The hard category comes to 43 hours per week since last April. That includes computer coding and writing up...
  27. F

    Calculating Number of O2 and N2 molecules per m^3 of air

    Homework Statement Part A: Calculate how many mocules per cubic metre in air at 27°C and at a pressure of 1.1 atm (1atm is 1.01 x 10^5) Part B: What is mass in grams of 2.4m^3 of this air. Assume that 75% of the air is N2 (with molar mass of 28 g/mol) and 25% O2 (with molar mass of 32 g/mol)...
  28. ellipsis

    Minimizing systems of boolean functions as per specific gate costs

    I've been grappling with this problem for a long time, but I think someone on this forum may know about this. Minimizing the joint number of products of a system of boolean equations is well-studied, and has various software implementations. Those are the Quine-McCluskey and Espresso...
  29. Ritzycat

    KJ per hydrocarbon "empirical formula unit"

    Homework Statement A sample of a hydrocarbon is combusted completely in O2(g) to produce 19.65gCO2(g), 4.023gH2O(g), and 280kJ of heat. Calculate the value of ΔH∘f per empirical-formula unit of the hydrocarbon. Homework Equations None I know of The Attempt at a Solution Previous calculations...
  30. O

    Speed loss per second due to air resistance

    Is there a formula covering this? (not including free fall/gravity) I have the drag coefficient, velocity and every other variable I think I would need for the object in particular.
  31. M

    Measuring varied power per revolution of a bicycle crank/chainring

    A bicyclist applies varied force and velocity on their pedals as it goes around one revolution. The power distribution over one revolution is like two waves with the higher power being made on the downstrokes. The push through the bottom/top produces the lowest power. The question is does...
  32. E

    Revolutions per second for hydrogen molecule

    Homework Statement The distance between the both nucleons in the H2 molecule is 0.0741 nm The energy for the 3 lowest radiation levels of the molecule are: ##E_{0}=0 \\ E_{1}=0.0151 eV \\ E_{2}=0.0453 eV## How many revolutions per second does the molecule rotate with in the different states...
  33. marcus

    Rarely asked question: converting 1/(Hubble time) to km/s per Mpc

    A couple of questions came up from different people and I thought I'd respond here in case anyone else might be wondering. First, not to confuse age of universe with Hubble time. Just coincidence that they are near. When you look at Jorrie's calculator (Lightcone link in my sig) you see we...
  34. skulliam4

    Rotations Per Minute Needed to Balance a Top

    I have little to no experience with this area of physics, so don't assume I know certain things. A cone is spun (with the tip down) at a constant, not decreasing, RPM (Rotations per Minute). What is the minimum RPM for it to stay there without falling, and (if possible) the minimum RPM necessary...
  35. D

    Energy per second transferred by the resultant wave

    Homework Statement the energy transferred per second by a progressive waves is directly propotional to the square of its amplitude, if two waves are in phase and superposed, the energy per second transferred by the resulatant wave propotional to A.) the sum of amplitude. B). The diffrenece of...
  36. F

    Mobile Phone Tower Question - Wave Equation and No. of Photons Per Sec

    Homework Statement A mobile phone signal with a frequency of 1945Mhz is being broadcast from a transmitter with a peak output of 3kW. A: What part of the EM spectrum is the signal. Classify it in terms of its orientation of oscillation and propagation. B: Write a general equation for the...
  37. V

    What is the solar constant in certain area of earth per day?

    Homework Statement The solar constant, the amount of solar energy reaching the Earth per unit time and area above the atmosphere and an element of area perpendicular to the direction from sunlight is 1.36 kW / m². For an element of area whose normal makes a angle q with the direction of...
  38. C

    How Many Electrons Calculate a Charge of -1.00 x 10^16 C?

    Homework Statement Two tiny, spherical water drops, with identical charges of -1.00 x 1016 C, have a center-to-center separation of 1.00 cm.(a) What is the magnitude of the electrostatic force acting between them? (b) How many excess electrons are on each drop, giving it its charge...
  39. O

    Amount of solar energy per day in a given location

    Hi, I'm trying to find equation for an amount of solar energy that given place (of some latitude) on Earth's surface receives during a given day. I know it can be derived by using basic geometry, but I just need it for some application and don't want to waste time and risk mistakes. So if you...
  40. K

    Automotive Can the horsepower of a car be given per cylinder ?

    say a car has 400 horsepower at the fly wheel with a V8. can you divide 400 by 8 to give 50 hp of power transmitted by each piston ? Just for a rough estimate, does it even come close to the real power transmitted by each piston or is way far off and wrong ? The reason why I think of this way...
  41. S

    Steps per wavelength in mesh density

    Hi Could anyone explain to me the concept and significance of mesh density as a function of steps per wavelength? I am asking this in context of a frequency domain EM-solver. Thanks
  42. R

    How to get the volume per atom when given the unit cell size?

    1. estimate the fermi energy for lithium... the crystal structure of lithium is a bcc with a unit cell size of 3.5*10^-10 m [b]i need n, which equals N / V. if i divide by per atom, then i get (N/atom) / (V/atom) = valance / (V/atom). my question is how to get the volume per atom...
  43. A

    MHB Linear Equations - Cost per Pound of Coffee Beans

    My problem is: A coffee house blended 18 pounds of espresso flavored coffee beans with 17 pounds of vanilla flavored coffee beans. The 35 pound mixture cost \$306.50. A second mixture included 19 pounds of espresso flavored coffee beans and 15 pounds of vanilla flavored coffee beans. The 34...
  44. A

    Calculating average inflation rate per year

    Homework Statement An economist has predicted that for the next 5 years, annual inflation will be 8%, and then there will be 5 years at a 6% inflation rate. This is equivalent to what average price change per year for the entire 10-year period? Homework Equations The Attempt at a Solution...
  45. H

    Dielectric test as per IEC for Low voltage panels

    Hello guys, I was searching for what voltage does IEC standard call for Di electric test that should be done to low voltage panels? is it 2.5 KV for 1 minutes? If yes how how low voltage cable rated 600/1000 V can withstand 2.5KV without insulation failure?
  46. M

    How do you calculate the theoretical packs per minute of a machine

    I am wanting to calculate the theoretical packs per minute of a machine. The machine pushes packs into a indexing conveyor and is transported along the conveyor and is cross pushed on to an exit conveyor. Each pack is 144 mm long and the machine indexes every 0.65s plus a 1.4 second dwell for...
  47. A

    How do I calculate the number of collisions per unit area in an ideal gas?

    I an ideal gas how do I calculate the number of collision per unit area? By collision I do not mean collision between the atoms but rather it is a problem where I know that a nucleation cluster of area A is in my gas, and I want to find the probability that it will get hit by an atom. I know the...
  48. J

    Calculating Magnetic Moment of Nickel per Kg

    Homework Statement For nickel, which has an atomic magnetic moment of 0.61 and an atomic weight of 58.7, calculate the magnetic moment per kilogram of the material Homework Equations None given The Attempt at a Solution Do I not need density to use formula for saturation...
  49. N

    How many drops per second keeps the protagonist awake? answer check

    Homework Statement Your roommate is an aspiring novelist and asks your opinion on a matter of physics. The novel's central character is kept awake at night by a leaky faucet. The sink is 19.6cm below the faucet. At the instant one drop leaves the faucet, another strikes the sink below and...
  50. J

    What is the angular speed in revolution per minute?

    Homework Statement You are consulting for an amusement park that wants to build a new "Rotor" ride. In order to increase capacity, they would like to build a unit with a 14.2-ft diameter. The Rotor should provide a centripetal acceleration of 3g. What must be the angular speed in revolutions...
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