Per Definition and 545 Threads

Homework Statement Which of the following products of ratios gives the conversion factors to convert meters per second (m/s) to miles per hour (mi/hr) Homework Equations a. [5280f/mi] x [12 in/f] x [2.54 cm/1 in] x [100 cm/1m] x [3600 s/1h] b. [5280f/mi] x [12 in/f] x [1 in/ 2.54 cm]...

Homework Statement The frequency of a vibrating string is set to 15, 20, 25, 30, or 35 Hz and the length needed to attain a standing wave (mode 1) is recorded. A graph of frequency versus 1/L is recorded. Calculate the mass per unit length of the string. The resulting graph has the...

thrust is the ability to move a 1 pound object at 32 feet per second per second. What does per second per second mean? Does that mean for every second, the object has moved 64 feet in a given direction? if air molecules are moved at 3200 feet per second per second to deliver 100 pounds of...

This is what you get if you compile numerous attractive females and then take all their features to come up with archetypal faces that is supposed to best represent the group they belong to.

I'm can picture acceleration but when it comes to the quantity of acceleration (meters per second per second) I'm lost. I just need a simple explanation of what m/s/s means.

gas flow rate has units of "sccm" that standard cubic centimeter per minute. what does "standard" means here? how is derived? if there is gas flow of 1 sccm then how much gas flows in cubic meters?

Hi all, I would like to ask a question regarding lasers and resonators: If I have a solid-state laser, and I know the following information: The gain medium diameter, it's length, population difference between the energy levels, gamma-alpha (r-a), broadening, wavelength, spontaneous...

Homework Statement I have been wondering about temperature and it's relation to kinetic energy I didn't study thermodynamics so I hope that replies could be simplified.I am trying to think about the perfect gas law to relate kinetic energy per molecule to temperature, and I want to know if I...

Just wondering.

Which of these have higher output per square unit*, phototransistors, photodiodes or APD photodiodes.?

http://europe.theoildrum.com/node/6638" has a chart that claims that the burning of methane yields 360 g of CO2 per kWh of energy released. I decided to check that, but I'm not getting the same answer they suggest. Here's what I did: CH4 + 2O2 = 2H2O + CO2 -74.87 + 0= 2*-285.83 + -393.509...

1. Fluorine compounds are added to water, the concentration being 0.90 ppm. a. What amount of fluoride present 1.0g of water? Solution- (just need to know what the number mean) Divided 0.90 pm by 1,000,000, which I assume is the grams of substance per kilogram? Then divided that...

Homework Statement An owl has good night vision because its eyes can detect a light intensity as small as 4.5 10-13 W/m2. What is the minimum number of photons per second that an owl eye can detect if its pupil has a diameter of 7.5 mm and the light has a wavelength of 503 nm...

I want to know how much energy is required by an average individual per day for his survival, assuming he is doing normal work. is there any rough estimate? (say some thousands of joules !). I like to know this rough value and I want to convert this is to electrical equivalent (i.e, in kWhr). In...

Homework Statement 1.A long, thick (cylindrical, solid) wire of radius 3 mm carries a total current of I1 = 100A that is uniformly distributed over its cross-sectional area. The current is in the +z direction. A second, thin wire runs parallel to the axis of the thick wire and is located at a...

Homework Statement The NIF will use extremely powerful lasers to attempt to implode a D-T target and thus initiate nuclear fusion. One pulse of the lasers will only last for 1 nanosecond, but the total energy is expected to hit 1.8 megajoules. The wavelength is in the near ultraviolet, 350 nm...

http://www.petapixel.com/2010/04/26/apollo-11-launch-at-500-frames-per-second/ High speed footage of the Saturn V's engines starting and lift-off with a very informative technical commentary.

Dear Physics friends! I would be very grateful if you could help me. I am currently working on my master thesis and I have the following question: The overall annuitized capital costs of a distribution grid amount to: 900 USD per kw and year. How do I get the costs per kwh? Thanks a lot...

Why is the number of electrons per unit volume , n fixed in a conductor regardless of the temperature while its not in semiconductors ??

the question is like this: Calculate the activation energy needed to create a single vacancy in aluminium, given: T= 500 Celsius Density (500 Celsius) = 2.62 gr/cm3 n = 7.57e23 m-3 Mw (Al) = 26.98 gr/mol I know these Formulas: n = N*exp (Q/kT) (k = boltzmann's constant) N =...

Homework Statement Prove that the number of turns per length on a solenoid is equal to 1/(diameter). Homework Equations A= 2(pi)(R) The Attempt at a Solution number of turns= length/(2pi*radius) number of coils per length=(length/(2pi*radius))/length number of coils per...

Homework Statement Two wires have current both running in the positive x direction as shown in the diagram with I1 = 13.9 amps and I2 = 4.5 amps. They are separated by a distance of d = 4.7 meters. A third wire with I3 = 10 amps is placed somewhere between the two wires with current running...

before i start i wanted to make it clear that this is NOT homework. its just a quick question which puzzled me and my friend In the shell model of the nucleus. i found a statement that said that since both neutrons and protons are fermions, there are restricted to 2 of each at each energy...

Homework Statement An LED emits a light beam with a power of 10 mW. The wavelength of the light is 420 nm. How many 420nm photons are emitted per sec.? Homework Equations E=hc/lamda is 2.95E-9 P/E= Photons emitted per sec. (10*10E-3)(2.95E-9)=2.952E-11 The Attempt at a...

If a student spends roughly 28 hours per week studying, and has 13 units , would you say that this is enough study time for the average person? With classes that are math, science related. This pertains to a student at a 2 year college? Do you believe it would it be different for a...

Hi experts, :cool: Is it possible to form a h-bridge using 2 spdt relays? What i can find on the net are h-bridges using 4 spst relays or using other types of relays. sincerely Ramone

Homework Statement The coaxial cable from a television or other device has an inner conductor with diameter of 1 mm and the shield of diameter 5 mm. Assume a plausible value for the dielectric constant (3 ≤ κ ≤ 5) of the dielectric separating the two conductors and calculate the capacitance...

Could someone please explain to me as to why the binding energy per nucleon is lower for atoms of low mass number as compared to the atoms in the middle zone of the binding energy per nucleon versus mass number graph? My conceptual issue lies in the fact that when the mass number is low the...

20 Liters per cubic meter of rain? A weather report for Chiclayo Peru said we received 20 liters per cubic meter of rain yesterday. How many inches of rain would a New York weather report say we received? Thanks. Tom

So to the students or former students who are in electrical engineering majors, how many hours per week outside of class do you study? Or did you?

Does the theory say that an electron is a single vibrating string? How many parameters are needed to describe that string? Does the theory say how long the string is?

I realize that there are numerous factors to be considered when attempting to calculate something like this as no two people are alike, work environments differ, etc, but what I am trying to find out is roughly even, how much physical work (FxD=W) an average person can do in a specific time and...

How to write "this per that" in mathematical terms? What is the mathematical equivalent of saying, for example, meters per second? If we want to say that something moves with the rate of 50 meters per 30 seconds--do we write this as a fraction or as an equation, or we can write as both? I...

I'm looking at a multiple choice test here and here's one of the questions Q.) Your hair grows 5mm per week. What is its speed in m/s? I calculating everything to appropriate units and got time = 604800 seconds length = 0.005 metres then to get the rate of metres per second I divided 0.005m /...

Hello guys. I have issues understanding a rather simple physics concept and I hope you can help me out. I've tried asking help from several people, but nobody was able to isolate the problem. For constant acceleration, it is said that d=(Vi+Vf)/2*t. d being distance, Vi is initial velocity...

When do we run out of uranium? How much is used per year? How much is in stock piles? How much is in deposits that we can afford to extract?

Homework Statement The question asks for us to go around our house, figure out the power usage of different devices, based on the estimated time use of these devices and calculate the total power usage per month. Homework Equations Energy = Power X Time Power = kW Time = hours...

Homework Statement A guitar's E-string has length 65 cm and is stretched to a tension of 85 N. It vibrates at a fundamental frequency of 329.79 Hz. Determine the mass per unit length of the string. 1Your answer is in kg/m Homework Equations (mass per unit length) = (tension) /...

If I've read this correctly, it seems the LHC will be colliding beams at 7 TeV each, producing a total collision energy of 14 TeV. The previous record was approximately 950 GeV at LEP/Tevatron producing a total collision energy of 1900 TeV. When the LHC starts colliding early next year (perhaps...

Hi all, i have a critical question. You have a point source (radioactive)..that emits 100 gamma per second. Now if you place a metal or foil (e.g., Al)..will the no. of gamma reduces? If it reduces how to calculate..based on beer law..(if we know the attenuation coefficient of that metal and...

Homework Statement The circumference of the collider is 26.66 km, and there are 4 equally spaced points where the beams collide. A collision takes place every 22microseconds at each one of the collision points, with 4 bunches in each beam. The average current per beam is 3mA. I...

What I'm looking to understand is why fission and or fusion result in the release of energy. I understand that: By looking at the Binding Energy per Nucleon Curve, due to the strong force acting at very small length scales and falling off as 1/x^3 and the electro-magnetic repulsion of the...

A potter's wheel moves uniformly from rest to an angular speed of 0.23 rev/s in 29 s.

1. Homework Statement [/b] Suppose in the figure that the four identical currents i = 13 A, into or out of the page as shown, form a square of side 64 cm. What is the force per unit length (magnitude and direction) on the wire in the bottom left hand corner? (N/m) Take the positive y direction...

Homework Statement You are planning to install a home video studio. A very important piece of information is missing from the specifications. You must find the capacitance per unit length for a coaxial cable. The cable has an inner radius of 2.0mm and an outer conductor 4.0mm in radius...

Homework Statement A bicycle drives on a straight road with a velocity v = 18 km/h. How many turns (rotations) of peddles per second must be carried out by cyclists, if the radius of the wheels r = 35 cm, and the ratio of the radii of front and rear gear wheels is 2:1? Homework Equations I...

Hi, I am trying to calculate how many electrons I need to confine in one cubic centimeter to make the pressure on the "walls" 1psi. I've tried the equation for the repulsion of two charges, but we're talking about trillions of electrons here and they're all pushing on each other however...

Hello, My question in this. If you have a system where two rods (different moduli of elasticity and different cross sectional areas, but equal in length) are compressed uniformally by a load, how do you calculate the compressive deformation in the rods. The compression of both will be...

Hello, Can someone help me with a formula for calculating a tire revolution per sec/min/hour taking as reference the air valve? The variables are tire size and speed in km/h. Thank you anticipated.

1. Homework Statement [/b] You are planning to install a home video studio. A very important piece of information is missing from the specifications. You must find the capacitance per unit length for a coaxial cable. The cable has an inner radius of 1.1 {\rm mm} and an outer conductor 3.1 {\rm...