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. I

    Magnetic Force Per Unit Length

    Homework Statement A packed bundle of 100 long, straight, insulated wires forms a cylinder of radius R = 0.600 cm. If each wire carries 4.50 A, what are the magnitude and direction of the magnetic force per unit length acting on a wire located 0.200 cm from the center of the bundle?Homework...
  2. P

    Solving EM Wave Emission from Cavity at T: Power per Unit Area

    Homework Statement Basically, the problem states that a cavity at temperature T is emitting EM waves isotropically in all directions (with frequency distribution of Planck's Law). If the time averaged density is <e>, find the value of d<S>/dw where w is the solid angle and the quantity is the...
  3. J

    Chemistry Is Molarity simply moles per liter

    Is Molarity simply "moles per liter" Is Molarity simply "moles per liter"
  4. K

    Calculating Revolutions Per Minute of a Ball

    Homework Statement A boy whirls a ball on a string in a horizontal circle of radius 1.0 m. How many revolutions per minute must the ball make if its acceleration towards the center of the circle is to have the same magnitude as the acceleration due to gravity? Homework Equations a=v^2/R...
  5. Somefantastik

    Flux per unit projected area per unit solid angle,

    "flux per unit projected area per unit solid angle," L = \frac{\partial \Phi}{\partial \left(cos \Theta \right) \ \partial \Omega} What is this quantity? I mean, I know it's "flux per unit projected area per unit solid angle," how does the math work? I know it's not \frac{\partial...
  6. G

    Exploring GRB Occurrence and Galaxies Across the Observable Universe

    GRB's occur once per day. over 10 billion years that's 3650 billion bursts (in the observable universe?). I think there are said to be around 100 billion galaxies in the observable universe so does that mean that 36 bursts occur in each galaxy...
  7. K

    Importance of Low Resistance per Unit Length in Electrical Cables

    Homework Statement Some electrical appliances are used with long cables to connect to them to the electrical supply. State and explain 2 reasons why these cables should have a low resistance per unit length. The Attempt at a Solution well for the long cables, a low resistance per...
  8. T

    Capacitance per length of co-axial cabel

    Find the capacitance per length of a co-axial cable with a conductor of radius a and a thin shield of radius b.
  9. F

    Precession angle per orbit of perhelion precession mercury

    Many derivations of mercury precession angle per orbit \Delta\Phi, equate this to extra angle per orbit \delta in excess of 2\pi that is \delta = \Delta\Phi But I am getting this relation \sqrt{4\pi\delta}= \Delta\Phi from arc length of helix and circular orbit. What am I doing...
  10. K

    Charge carriers per atom in graphene

    Hello. I'm trying to find the individual contributions of carbon atoms to the charge carriers in graphene. In other words, I'm trying to answer "How many charge carriers does one carbon atom supply?" Here is what I've done so far: Taking the max. carrier density as 10^13 1/cm^2 and the...
  11. O

    Area efficiency of Miles Per Gallon

    My physics professor posed that question to us a while back, and he never gave us the answer. I tried solving it but I had no idea what units to convert it too. Does anyone have any ideas as to what the answer may possibly be?
  12. S

    Dimension of momentum per metre

    Considering momentum to be in units of \rm kg^1 m^1 s^{-1}, is there any particular attribute associated with \rm kg^1 s^{-1} (other than "momentum per metre")? Or perhaps the inverse \rm s^{1} kg^{-1}? Just curious.
  13. Ed Aboud

    How do you convert watts per meter squared to decibels?

    Hi. How do you convert watts per metre squared to decibels? I know you use logs but can't seems to work it out. Thanks for any help.
  14. S

    Calculate the average binding energy per nucleon

    a) Calculate the average binding energy per nucleon in the deuterium nucleus. b) The energy that binds an orbiting electron to the hydrogen nucleus is 13.4 eV. Calculate the ratio of the binding energy per nucleon to the binding per electron in deuterium. Which particle is held more tightly...
  15. N

    Question about electrons per shell

    why is it the maximum electrons per shell is 2,8,18,32,50 ... Wouldn't 2,8,16,32,50 make more sense mathematically? Are there any equations the show why this occurs?
  16. C

    Finding mass per unit length for stretched strng given tension?

    [SOLVED] Finding mass per unit length for stretched strng given tension? A transverse wave on a stretched string under Tension = 5N is defined by the equation: y(x,t) = 0.1cos(2pi/5(x - 10t) Find: a) amplitude = 0.1 m b) wavelength = 0.4 m c) angular frequency = 4 rad/s d)...
  17. K

    Find number of photons emmitted per sec?

    Hi, I have a question asking me to find the number of photons emmitted per second. I am given the information that the Gallium Arsenide diode laser emit 0.9 mW of power inside a CD player. The bandgap of the Gallium Arsenide is 1.42 eV. What equation is used to find this?
  18. F

    Number of electrons per cubic metre

    If you stretch a wire, increasing its length will the number of electrons per cubic metre decrease? Assuming the Cross sectional area stays the same. The number of electrons will surely stay the same, and won't increase just by you stretching it, and the number of cubic metres has increased, so...
  19. L

    Calculate the resistance per meter

    Homework Statement Calculate the resistance per meter at room temperature of a constant wire if diameter 1.25mm. The resistivity of constant a at room temperature is 5x10^-7\Omega{m} Homework Equations I'm not sure, but I think this is the right formula: R = \frac{Pl}{A} The...
  20. C

    Photons per second from a radio transmitter

    Homework Statement A radio transmitter radiates at the power of 10 kW at a wavelength of 100 m. How many photons does it emit per second? Homework Equations E=hv, and some other equations of beginnings of wave mechanics. The Attempt at a Solution I had no idea where to start.Please do not...
  21. N

    What Does 'Per cm' Mean in Chemistry and How is it Used in Spectroscopy?

    I don't understand "per cm" Chemists seem to use the "per cm" (cm^{-1}) scale for spectroscopy. I'm use to dealing with THz. Can someone please point me to a resource or explain where per cm is used and how to convert between different common units?? I know you just take the wavelength, put...
  22. N

    Astrophysics - How much CMB-photons do you absorb per second

    Homework Statement 1) Calculate approx. how many Cosmic Microwave Background-photons that you would absorb per second if you were in space. The Attempt at a Solution Ok, I know that the CMB-photons fit with a blackbody spectrum with T = 2.725 K. So the total amount of photons I find by using...
  23. L

    What is the relationship between Rayleighs and counts in a CCD?

    How can I find the number of Rayleighs per count if I know the column emission rate, radiance, irradiance, #photons per pixel and #photoelectrons per pixel? I'm totally lost in this one, please help!
  24. H

    Calculate the charge per length for the capacitor

    Homework Statement I REALLY REALLY REALLY NEED YOUR HELP - I TRIED TO SOLVE THEM BUT IT'S NO USED I HAVE 5 PROBLEMS (I NEED YOU TO HELP ME SOLVE THEM EVEN IN ONE PROBLEM ) ------------------------------------- Q1 A cylindrical capacitor consists of a solid inner conducting core with radius...
  25. E

    Heat Capacities and Derivatives of Fugacity with Volume per Particle

    Homework Statement This question refers to Pathria's Statistical Mechanics textbook. In this problem, there is the equation: \frac{C_P}{C_V} = \frac{\left(\partial z /\partial T \right)_P}{\left(\partial z /\partial T\right)_{\nu}} where z is the fugacity and \nu is the volume per...
  26. R

    Calculating Uranium-235 Usage in Nuclear Power Plants

    Homework Statement Given that the average fission produces 200 MeV in energy, and that nuclear plants have an efficiency of 33%, how many fissions take place each second in a plant producing 1000 MW of electricity? How much uranium-235 is being used per day? The Attempt at a Solution I've...
  27. V

    How does the binding energy per nucleon of a nucleus affect its stability?

    How does the binding energy per nucleon of a nucleus affect its stability?
  28. C

    Medical How can some people stay healthy with just three hours sleep per day?

    From time to time we read about people who sleep three or four hours per day day. E.g. Thatcher, Churchill, Arafat, Edison etc. all slept just a few hours per day (about four hours if I remember correctly)...
  29. G

    How many lines per centimeter does the grating have?

    Homework Statement The light shining on a diffraction grating has a wavelength of 488 nm (in vacuum). The grating produces a second-order bright fringe whose position is defined by an angle of 8.02°. How many lines per centimeter does the grating have? Homework Equations d sin q =...
  30. B

    Calculate Bullets Per Minute for Machine Gun and Man

    This was a two part question, the first part I was able to calculate. Question Part 1: A machine gun fires a stream of bullets into a block that is free to move on a horizontal frictionless tabletop. Each bullet has mass 66 grams; their speed is 930 m/sec, and the block a mass of 7.36 kg...
  31. S

    Oh jesus. potential difference problems help per favore

    1) You have a potential difference of 6 volts. How much work is done to transfer .19 coulombs of charge through it? Answer in units of Jules. 2) Through what potential difference would an electron need to be accelerated for it to achieve a speed of 6% of the speed of light(2.99792e8)...
  32. T

    How Do You Calculate the Number of Photons Per Pixel in a CCD?

    A fresh question. I want to find the number of photons falling on a pixel in a CCD. A very simple model: * bigger source area gives larger response (A_s ) * when object farther away, smaller response: \frac{1}{R^2} * bigger detector area gives larger response (A_d ) * size of the lens is...
  33. C

    How much energy is saved per airplane

    Homework Statement An airline executive decides to economize by reducing the energy, and thus the amount of fuel, required for long distance flights. He orders the ground crew to remove the paint from the outer surface of each plane. The paint removed from a single plane has a mass of...
  34. A

    12 Toppings, 4 toppings per pizza, How many total?

    Homework Statement You can order a pizza with up to four toppings (repetitions allowed) from a set of 12 toppings. The order of the toppings is unimportant. How many different pizzas can you order? (To clarify: this UP TO four toppings, so a completely empty pizza is fair game, as is a pizza...
  35. C

    How many pounds per square inch is exerted on the large block of steel

    Homework Statement Don't know how to calculate this. Not sure I care either, but I figured you people do care and know. I'm having a little dispute with someone about pounds per square inch of say an object moving at a high rate of speed on impact with say steel. So here is the scenerio. Let's...
  36. R

    Maximizing Profit Per Hour: A Day Trader's Strategy to Maximize Income

    A stock day trader has a winning system and he wants to maximize his profit per hour. He has found that when he trades 5 hours a day, 90% of the time he will make 2 points profit or less and 10% of the time he will make more than 2 points profit. He knows that to earn the maximum total amount of...
  37. B

    Same string, different mass per unit length, whats the wavelength?

    [SOLVED] Same string, different mass per unit length, what's the wavelength? *oddly I can't edit the original title? Homework Statement A string is made of two materials of different mass per unit length. On the left side of the string, the mpu is given as well as its wavelength. On the...
  38. P

    News Highest gdp per head of population

    Which country has the potential to have the highest GDP per head of population if its economy was run perfectly? Can one country run a perfect economy if its trading partners do not? Is there a country that can get by on its own with internal markets?
  39. M

    How to study 12+ hours per day without hurting your

    This is a serious question, even though it may sound funny: How do you study 12+ hours per day without hurting your bum? I have a nice office chair, well-padded, yet my bum hurts from my 12+ hour daily studying (literally sitting on the chair for 12 hours per day). Anyone else go through this...
  40. M

    How many hours per day does a full-time professor spend on pure research?

    Is it more or less than 6 hours per day?
  41. V

    Optimum speed for mileage per gallon

    I imagine that this magnitude is dependent on a lot of factors, but does anybody know a good source to get the relationship betwen speed and mpg for at leas families of cars?
  42. S

    Electromagnetism Problem, electric charge per unit volume.

    Homework Statement The atmostspheric electric fields at heights of 100m and 1000m above the surface of the eartg are 110 v/m and 25 v/m respectively and are directed downwards. Evaluate the averge electric charge per unit volume in the atmostsphere between these heights. Express your result...
  43. ~christina~

    Revolutions per sec (centripital acceleration)

    [SOLVED] Revolutions per sec (centripital acceleration) Homework Statement As their booster rockets seperate, space shuttle astronauts typically feel acclerations up to 3g where g= 9.80ms^2. In their training astronauts ride in a device in which they experience such accelrations as...
  44. R

    Electric Field for infinite sheet of uniform charge per unit area

    OK. In my book it says that for "any point" the Electric Field Magnitude for a Infinite sheet of charge with uniform charge per unit area is \frac{\sigma}{2\epsilon_{0}} , and for a wire of infinite length the Electric Field Magnitude is E = \frac{\lambda}{2\pi\epsilon_{0}r} where r is the...
  45. B

    Uniform angular acceleration - degrees per second?

    Homework Statement A wheel is subjected to uniform angular acceleration. Initially its angular velocity is zero. During the first 1-s time interval, it rotates through an angle of 88.6degrees. (a) Through what angle does it rotate during the next 1-s time interval? (b) Through what angle...
  46. B

    Courses How Many Courses Should I Take Per Semester?

    Do you take all courses prescribed for the particular semester (full load) like in my case 6 courses for this semester or you take less; like 4 or 5 or maybe 3?
  47. C

    What are the approximate costs for operations on common x86 chips?

    As a first step to optimizing code, I like to think about faster ways to do things. Algorithmic improvements are far better than minute improvements to code, or even use of inline assembly, in general. But most optimizations beyond common subroutine elimination and its ilk substitute...
  48. P

    Question-binding energy per atom

    Thanx to all who helped me with my first posts. Now on to bigger and better things! The Binding Energy Curve shows Helium at about 7. As there are 4 nucleons in Helium, would the atom have a total binding energy of 28? Iron has a binding energy of about 8.75, so would it's total binding...
  49. Q

    How to calculate acceleration per second

    the law: a1 = G(m2/r*r) to calculate acceleration with gravity, gives the m/s*s. (i don't know how to type the square sign) but how can u calculate how many m/s an object gains in a certain time?
  50. J

    Can time really be measured accurately with just 15 minutes per minute?

    What goes at the rate of 15 seconds per second?
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