Hi Definition and 264 Threads

Hi all Why does a molten metal solidify with decrease in temperature. or in other words why is a closed packed structure more stable than an amorphous liquid melt. I have read that the free energy below melting point is lesser for solid state than that of for liquid state at the same...

Hi In the Diffraction Handbook http://gratings.newport.com/library/handbook/chapter6.asp#6.2.4 it says: A grating used in the Littrow or autocollimating configuration diffracts light of wavelength λ back along the incident light direction (Figure 6-4). In a Littrow monochromator, the...

Homework Statement With a lens with f = 25 cm, we want to project an image that is 5 times bigger than object, so M = 5 - Find the image distance s' - Find the image height Hi Homework Equations 1/f = 1/s + 1/s' M = s'/s = Hi/Ho With: f = focus distance of lens M =...

Perfect Number Program Java Methods A perfect number is a positive integer equal to the sum of all its divisors (including 1 but excluding the number itself). For example: 28 = 1 + 2 + 4 + 7 + 14 According to Euclid, any solution to (2n-1) that results in a prime number will indicate that...

hi Our teacher told us the following: F = m * v² / r = m * 4 pi² / T² * r = m * 4 pi² / k * 1 / r² = c * m / r² F = y * mM / r2 Why is there the k and 1 / r² and later the c?

hi guys, i was studying on transformers losses, i need help in some problems. why open-circuit test show only excitation losses and not i2R losses.. thanks...

Hi guys. Imagine how dumb I feel for never having heard of this equation before today. I have a serious exam coming up and the only thing I know is that this will definitely be coming up. I know it's applications, but I have no clue how to apply it proper. There are no calculators allowed...

Hi guys. I'd like to make an introduction somewhere but there doesn't seem to be a forum for that here. Basically I am an older student who, despite having low grades all throughout school, always loved science. I decided to go back to adult school to upgrade my marks and then go to university...

Hi! This is the definition of simultaneity I was taught: Two events that are simultaneous in one frame of reference need not be simultaneous in a frame moving relative to the first frame. I'm wondering if this concept only applies to relativistic phenomenon, and if not, would you happen...

Hi all, I am reading a paper related to astrophysics and I am stuck in a step in a calculation. It is about orbiting gas in a spiral galaxy and it calculates the errors in the fitted rotation velocity if one of the viewing angles is incorrectly estimated. My problem is that I don't understand...

hi why do many dyes who have a conjugated system of delocalized electrons absorb, not a particular wavelength, but often a whole range of wavelenghts? so if there is a dye, that absorbs let me say all wavelenghts between 640-680nm. how is this possible? for me, this would mean, that...

Hi PF, I have been working quite heavy shifts of late being a truck driver but enjoy a few cans of beer when I can and wanted to know if there is anything I can put together at home that will give me a simple indication of my alcohol reading i.e green or red light. How would I go about...

I am a nerd, youngish, not old, studying the Physics. My name is Vulcan. Says it all. Posted a little to see if this forum was for me; seems so so far. :smile:

Hi Folks, I am currently reading Brian Greene's 'The Fabric of the Cosmos' which is excellent. I am trying to get my head around the Delayed Choice Quantum Eraser in this book. Is there a website link I could follow up that explains it well? I have already looked at...

Hi guys ,I have to give a presentation on UAV's ,i have some experience with RC planes but that's about it .Now there's few things about UAV's in particular that I'm unaware of ,if you could help me it'd be of great help . GROUND DATA TERMINAL AIRBORNE DATA TERMINAL AIRBORNE DATA RELAY...

Hi, How do I find the height of the triangle , the triangle is set at 30 degrees and the length is 5 meters any help would be appreciated.

Hi everyone! I was thinking of you all today and thought I'd drop in and say hi and let you know I'm still alive and well. I thought of you all because I'm working a faculty for a summer program with our state's honors students, and one of the RAs, who is a physics major, did a demo for the...

Hi I have a question about POVMs im confused as to how they correspond to actual measurements we do in a lab, and how non-orthogonal measurements fit into this context. For example we have some POVM with elements E_i. I read in Nielsen and Chuang that we do a measurement and get outcome m...

Hi everybody, this is my first post. So sorry for the possible trivial question. Can someone explain me what is Y-bjorken? And what is the difference with X-bjorken? Thanks

Hi, I have attached a Di-electric study graph of Copper. a) How can I do the di-electric measurement from this graph? b) How can I measure the loss of di-electric? c) How can I measure the di-electric constant? d) The graph gives the result which is linear. Is it essential that the...

Hi folks! I am new to this forum and have a question that I hope someone can answer. I have 4 circular holes, 3", 4", 5" and 6". I am covering the holes with 14 gauge sheetmetal. The sheetmetal is circular also and overlaps the holes 1" all the way around. My question is, how many pounds would...

Hi all, First up, I should make the point that I am not a physicist. I studied physics at school, but can't say I was ever any good. As such, this question may have a very obvious answer that I have missed. That said, it has been puzzling me for a while so I thought I would ask a forum of...

I think I need some guidance with being polite. If my neighbors are outside talking and they get quiet as I come out of my car, does that mean I am supposed to say hi? Sometimes people get angry at me for not saying hello, and then sometimes they get angry when I say hello, so I don't know...

hi everyone. I am a beginner to matlab, i want to calculate the Fourier series Coefficients of a discrete periodic signal with period N=100 and plot it. the signal is real and even

Hi Guys, When the eye sees an object, there has to be light reflecting from or emitting from the object itself. How does this happen with a hologram? Does the interference pattern actually scatter the light so we can see it?

Hi, :smile: Please take a see on this Google Doc: https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B_XrsbDdR9NEZTY5MWU3NjUtMzk5NS00MDRiLWFjMjgtNTVjY2IwNGUxNWZk&hl=en&authkey=CPWM-YUI Can you help me with the highlighted part please? I don't understand it. Perhaps you can...

Hi, as part of a project I needed a slim (<10mm) small diameter (<30mm) through hole absolute encoder that works at 100 degC. I wanted this to be able to determine a motorized valve position, so it needed to slip onto the gearbox output shaft between the motor and the valve. Anyway, I...

Hi, the wikipedia article on fermium states that it is the last element that can be synthesized by neutron bombardment but decides not to explain why. Can anybody give a layman's explanation? Thanks.

hi guys,does anyone knows what is the physical interpretation of second(third, fourth,...) derivative?

Homework Statement Two Questions: 1) A 9.0-kg ball is traveling to the right at 8.0 m/s until it impacts a 3.0-kg stationary ball. After the collision, the 9.0-kg ball is traveling at 5.61 m/s at an angle of 7.8º above the horizontal. Calculate the velocity of the 3.0-kg ball after the...

Homework Statement Using the graph below, what is the magnitude of the impulse provided to a 48 g tennis ball that is swerved due south? Also, What is the velocity of the ball when the racquet and ball separate? Homework Equations p=mv (I think). Fnet x delta Time = P (maybe)?The Attempt...

hi I'm an applied maths student i'd like to study about catenary.. where can i get details of catenary and its applications in detail?which book i can refer or is there any website i can go for?

hi guys i am new here , help me in "undescended testes" hi guys , i hope all here are fine and well . I have "undescended testes" and i know it is caused due to my over masturbation when i wan young , now i left masturbation some what , but still my testicles or improper in position ...

Click http://www.xtremepapers.net/CIE/International%20A%20And%20AS%20Level/9701%20-%20Chemistry/9701_s02_qp_1.pdf" for question. Question 33. The atomic Radii of Iodine is much larger than Chlorine hence the bond length of HI should be smaller compared to HCl. Apparently, it is not so...

Hi...I go by Fobio. Good to be here...and I thought I'd introduce myself. I'm a 30-something married banker who's into cars and amateur racing. In my high school years I did well in math and physics but did not pursue that in university. I've always had a interest in science to the point...

I have a project with two, separately wired high-power LEDs. LED #1 is a 1 watt LED rated at 3-4 Vdc at 350/700 mA LED #2 is a 3 watt LED rated at 2 Vdc at around 350/700 mA According to Resistor calculations, I get: LED #R1 = 4.7 Ohm, 2 Watt rating (for 700 mA) LED #R2 = 8.2 Ohm, 4...

Hi guys In my statistics book there is an example. They say that we see 3 occurrences of type A, and theoretically expect 7. This is a difference of 4, since we know that the standard deviation is 1.65 (they calculate it), then the difference is 2.4 standard deviations. Looking at a table of...

Homework Statement A train slowly climbs a 500 m mountain track which is at an angle of 10 degrees with respect to the horizontal. How much altitude does it gain? Homework Equations Looks a lot like the jogger one except you find change in y instead, right? Are we missing mass? Do I...

325*(0.8)^t=5 Can anyone help me please?

A simple of an unknown with plants decomposition of the sample produces 0.09. 48 G of C , 0.1264 g of O and 0.0158 g of H . What is the % composition of the compound ?

This greeting from a newcomer was posted out of place (in bibliography) so I copy here, to give J. his own thread. Please welcome. My comment: Jonny the core message here may actually belong in the "Academic guidance" forum up near the top of PF main menu. I will copy and highlight what I...

Hello~ I'm a "little" girl studying in secondary 6 (7 after 1/9) in HK~ I love physics very much~ I want to major in electrical engineering or physics in university ^^ I find this forum is quite useful so I registered to be a member~ Hope you guys can understand my poor english~ ^^

Hi! I'm ZxWhatever (Short for Zxblqcktptydfkjsplkn, my username elsewhere). This is my first post here. I'm going into high school next year, and physics has always fascinated me, specifically quantum physics. You may think this is WAY to early to be thinking about a science fair, but I want...

hi colleages. is Bernoulli-Euler theory valid in the dynamic analysis as following: M/EI=1/R where, M= moment EI=stiffness R= curvature is this equation valid when M becomes a function of x and t, as follows: M(x,t)/EI=1/R

Hello Back again for another round of making the "resonant electrostatic water capacitor" aka water fuel cell aka hydrogen generator.kl The "[URL out"]instructions[/URL] say to use a high impedance circuit, which pulses high voltage to the electrodes at a very finely adjustable rate. Two...

Hi! There is no structural/civil section! Is structural/civil not highly regarded in America? For you civils/structurals: What would you recommend as a good speciality in civil/structural engineering, and why? I'm not looking for the usual listings of specialities, but if anyone has any...

hi everyone... i am dong my project designing a 3d solid state hi everyone... i am dong my project designing a 3d solid state accelerometer.The accelerometer should detect and measure steps. Can anyone of you help regarding the design of it...

I do not know if works the same everywhere, but as a freshman in university I am really new to this. My professor gives us assignments, even-numbered assignments, on our homework. Now being the youngest person in my class and not knowing anyone is a disadvantage. Because those assignments my...

Hi, my name is Luis and I am a High school student currently enrolled in Foothill High School. I need to interview someone in the profession of Engineering, someone who is willing to speak face to face and discuss the advantages/disadvantages of being an engineer.

Hi, what is the use of PFC?