Per Definition and 545 Threads

[FONT="Georgia"][SIZE="3"]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 =...

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...

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...

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...

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!

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...

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...

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...

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

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)...

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 =...

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...

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)...

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...

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...

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...

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...

[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...

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?

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...

Is it more or less than 6 hours per day?

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?

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...

[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...

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...

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...

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?

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...

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...

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?

What goes at the rate of 15 seconds per second?

Does anyone have a chart of what a straight pipe flows in cfm? Like 3 inch inside diam.? 4 inch? Etc? Thanks:)

My intuition is wrong on many things, so I thought I would throw this question out there to see what everyone thinks. And hopefully some people with teaching experience will respond (of course everyone is welcome to respond). On average how many hours do full-time teachers (high school or...

Hi there, I am the administrator for an airsoft group based out of the Chicagoland area. Many of our members currently use mesh safety goggles of the sort used in arboriculture, wood chipping, and concrete cutting. These goggles do not have a specific impact rating (though the manufacturer...

Homework Statement What is the value of 3.0 coulobms per second in Amps? The Attempt at a Solution amps are coulombs per second, so its just 3 right? I just want to make sure this isn't some kind of trick. thanks for any input.

[SOLVED] Mass per Unit Length of Violin Strings Homework Statement Each string on a violin is tuned to a frequency 1.5 times that of its neighbor. If all the strings are to be placed under the same tension, what must be the mass per unit length of each string relative to that of the lowest...

Homework Statement Suppose a power plant delivers energy at 9.7E2 MW using steam turbines. The steam goes into the turbines superheated at 665 K and deposits its unused heat in river water at 298 K. Assume that the turbine operates as an ideal Carnot engine. a. If the river flow rate is...

Homework Statement I am looking for a conversion factor that will ultimately get me from units of lux (illumination) which is a weighted scale of light intensity, to watts per square meter, which is not weighted. Homework Equations None availiable The Attempt at a Solution I am...

Most batteries have a low voltage output like a lead acid +- 2.2V per cell And carbon + zinc have something like 1.5V and so it goes on. Can a battery have a high output voltage without putting it in series Example: I want a battery with 100V DC output per cell, does that exist or not...

Homework Statement What is the power of a machine that does 1800 N-m of work per minute? Homework Equations KE = m*v^2/2 V = sqrt(2KE/m) The Attempt at a Solution I don't know what N-m are... so I'm not sure what to do..

Homework Statement The combustion of the fuel gas butane is given by: 2(C4H10) +13(O2) --> 8(CO2) + 10(H2O) del(H)= –5760kJ/mol What mass of butane would be needed to produce 33440J of energy? Homework Equations The Attempt at a Solution First of all how do you interpret...

Hello everyone, this is a computer science/computer engineering problem... I had the following file that multiplies 2 matrices together, with 100 elements and puts it into a 3rd 100 element matrix. Well I used Simple Scalar to anlayize the CPI generated by the code and it also records the miss...

Hi, Homework Statement In a simple model of the hydrogen atom, the electron moves in a circular orbit of radius 0.053 nm around a stationary proton. How many revolutions per second does the electron make? Homework Equations F = (kq1q2)/r^2 = (mv^2)/r v = wr The Attempt at a...

I'm editing a school textbook and have suddenly discovered at the 11th hour that there is a difference between the U.S. cup (236ml), the Canadian cup (227ml) and the British cup (284ml) as well as conflicting results (such as Wiki) that define them differently again - U.S.=250ml, Canadian=240ml...

Hi there. In my homework, I had to calculate the variation of the pressure with the altitude for a classical gas. I know that I should calculate the density of particles per volume element. I found this pdf on the net (http://cannoli.mps.ohio-state.edu/phy847/phy847-p2.pdf) . If you see...

How much do you spend on clothes per year? looking through my wardrobe this morning i realized all mine are ancient, the only whistle and flute i had died of moth bite years ago, it seems i only ever buy socks.

A sample of blood is placed in a centrifuge of radius 19.0 cm. The mass of a red blood cell is 3.0 10-16 kg, and the magnitude of the force acting on it as it settles out of the plasma is 4.0 10-11 N. At how many revolutions per second should the centrifuge be operated? I converted 19cm...

Hey everyone, Just wondering if anyone could help me with my physics homework. It's my first time ever doing physics and I was always terrible at maths. It needs to be in soon so I'm kind of freaking out :frown: If anyone could either show me how to answer these questions or even pm I'd be...

Does the single-handedness of DNA and RNA indicate that life originated few times, if more than once? What might the sameness between early sequences (in bacteria, say) indicate in this regard?

I understand that the energy is in joules (?), but unsure of mass and velocity formats. I am trying to calculate the energy of an impact. Specifically, the heat energy (btu) resulting from various bullet impacts. Feel free to ask further questions if you need to know something else to answer...