Short Definition and 523 Threads

I've been thinking about this short story I read a while ago, and it's been bothering me. I can't remember any specifics that would help me search for it. Hopefully if I outline the plot someone here will recognize it, I think it was a fairly well known story. It was the not to distant...

Abstract algebra question. Given the short exact sequence $ 1 \longrightarrow N \longrightarrow^{\phi} G \longrightarrow^{\psi} H \longrightarrow 1 $ I need to show that given a mapping $ j: H \longrightarrow G, and $ \psi \circ j = Id_h $ (the identity on H), then $ G \cong N \times H. (The...

1. Invariants in field strength The first part of the question asked you to calculate the Lorentz scalars by contracting the field strength tensor (F) and it's dual (G): FF, GG and FG (index's omitted) and formed ±2(B²-E²/c²) and -4/c(E.B). The next part asked: Are there any other...

Homework Statement 2) 2 resistors, 42 and 64 ohms, are connected in parallel. The current through the 64 resistor is 3A. Determine the current in the other esistor and what is the total power supplied by the two resistors? Homework Equations The Attempt at a Solution 2) How...

1. Platinum is silver and shiny. Why? 2. Aluminum oxide can be either transparent, red or blue. How? 3. Quartz is transparent. Why?

Homework Statement 1) When a swimmer dives into water just before piercing himself into water, he stretches himself. Why? 2)In a tug of war if the parties on both ends of the rope apply apply equal and opposite forces on each other then how can one party win? The Attempt at a Solution...

A 20 year old Brazilian model with a bright future had her life turned upside down in just under a month. A rare blood infection compelled doctors to amputate her hands, feet, and removed two kidneys, and part of a stomach. She had 24 hours to live two weeks ago...

The problem is that a space heater develops a short circuit when to much current enters the circuit. The power supplied is 1500 W and the max current before short circuit is 15A. Firstly we have to calculate the resistance of the heater where I used P = I^2 R. But now we have to find the...

Homework Statement Solve the equation log x4 - log x3 = log 3x - log 2x I know the laws of logs and I cleared all the other log questions in seconds but I can't figure this one out Homework Equations I know that log x4 - log x3 is the same as log x4/x3 but what I was wondering is if...

Thanks again for the comments on my previous post. I've done some work narrowing the field of math schools. Note that since my previous post I've made a decision to weight schools in the south a bit more heavily than those in the north. Here is a list, along with my comments. AMS Group I...

hi, I have this problem I've been stuck with for a long time and i can't figure out what to do. if spherical coordinates are denoted (r,θ,ϕ) and cylindrical coordinates are denoted (ρ,ϕ,z), how do i express the radial unit vector in cylindrical coordinates, e(ρ), in terms of the spherical...

Homework Statement A copper bar is moved to the right while its axis is maintained in a direction perpendicular to a magnetic field as shown in Figure P31.28d (image d, bottom right). If the top of the bar becomes positive relative to the bottom, what is the direction of the magnetic field...

Hi there! I have some problems understanding the connection between high momentum transfer and short distance behavior. I know that the QCD coupling goes to zero as the momentum transfer Q^2 approaches infinity. Most introductory HEP textbooks say that this means that the quarks in the nucleons...

Is parkour suitable for tall men to practice? Will it add larger probability to tall men to get hurt considering taller men has lower bearing surface to body mass ratio?

Hi, I'm trying to perform a short circuit fault calculation on this transformer and load I have when a 3 phase bolted short (worse case) occurs. The transformer specs are below: Z(transformer)=5%, Z(cable)= .00306 + j.0027, Delta/Star 6.6kV/400V I can understand calculating the short circuit...

A railroad car has crates in it with a coefficient of .5 w/ the car's floor. The train is moving at 22m/s, how short a distance can it be stopped w/o letting the crates slide? Fnet = 0 because you don't want sliding. a = coefficient of static friction x gravity When I solved for a...

I have not yet read anything about special relativity, so these questions may be naive. Here are my questions (very much related to each other): 1) Is it assumed in the physics community that dark matter is really matter? If so, why? 2) Can't it be that "dark matter" is just a dent in...

Homework Statement What is the difference between an open circuit and a short circuit? Open circuit has no current, so does that mean any resistor in series with it, has no current ,so it can be ignored for analysis( v=ir so 0 current means 0 V) for finding let's say the Thevenin...

Hi everyone Books mention the Open Circuit and Short Circuit tests on a synchronous generator in order to determine its synchronous impedance. One observes that the Short Circuit Characteristic (plot of short circuit armature current versus field current) is a straight line all the way...

how to not short circuit an induction heating coil Just wondering about induction heating coils and how to not short circuit one. basically, if i hook up one end of the coil to the positive and one end to the negative (DC) i assume that i will be short circuiting the connection and also...

Homework Statement Let g(5)=-3 g'(5)=6 h(5)=3 h'(5)=-2 Find f'(5) for f(x)=g(h(x)) Find f'(5) for [g(x)]3 The Attempt at a Solution Find f'(5) for f(x)=g(h(x)) g'(h(x))*h'(x) g'(3)*-2 But I don't know where to go from there because I'm not given g'(3). Find f'(5) for [g(x)]3 I was thinking...

A 20 kg monkey holds on to a rope that passes over a frictionless pulley and is attached to a 20 kg bunch of bananas. The monkey starts to climb the rope to get the bananas. a. as the money climbs, do the bananas move up, down, or remain at rest? b. as the money climbs does the distance...

Homework Statement I am trying to write a short speech about angular momentum - aimed at kids leaving school and going on to university. I have started with a brief description of linear momentum, definition of vector, and them the fact that linear momentum is analogous to angular momentum and...

I'm currently studying mathematics at the undergraduate level and am required to conduct the following survey. I apologize if 'Career Guidance' is not the correct section for this, but it seemed the likeliest fit to me. Any responses at all would be greatly appreciated. 1.Please state your...

Hi, I have a short question about Nakahara's treatment about Laplacian's: page 294, section 7.9.5, equation (7.188). He calculates the Laplacion \Delta = dd^{\dagger} + d^{\dagger}d for a scalar function f. Every step is clear to me, except one; at the fourth line there is a factor of...

Assuming that all other conditions are the same, is a short person more stable than a tall person? Is the centre of gravity lower for a short person?

Take a laser source with small bandwidth centered around the average frequency (or wavelength) With an hypothetical external modulator that can switch as fast as we want, ca we make a pulse that is spatially shorter than 1 wavelength? If not? Why? What would that entail? Clearly the number...

Im learning math and physics on my own and I have had some problems when it comes to remembering how to do topics about math and physics. Currently I am trying to make more summaries, and a list of math and physics topics in order to remember more about them. Do you guys have any advice or...

Would somebody be kind enough to explain what exactly is meant when discussing short- or long-distance contributions/effects to branching ratio calculations?

http://www.cbc.ca/story/world/national/2006/05/26/short-prison.html?ref=rss Like Thompson, I am 5'1". I don't applaud the ruling. This is almost comical though. Prison is a danger to him, what about the child?

Hello All, I have short edge margin condition of 1.36D on one of the part.Actually 3 parts of aluminum are joined together by bolts and one part has short edge margin. All the parts have sufficient bearing strength.So if I understand right bearing failure occurs before...

I am looking for a suitable text for a short course that will be taught over a 16 week period. Students will take this nation-wide to compete for cash prizes and a college scholarship. Each year the subject matter is different and this year, it will be nuclear physics and chemistry. I am...

Just saw this short movie. Some good surprises. Make sure you watch the WHOLE thing.

I can see the lack of input is frustrating, i too am so frustrated about the lack of testable results, but that is of no concern, so long as there exists a way forward, what is the way we should go?

Can you do two PhDs in two different subjects? I am hoping that i can do a PhD in both theoretical/mathematical physics AND pure mathematics, is that possible?

If a full grown man in America is only five feet one inch tall, how much do you think his extremely short stature will affect his life? In what ways will being five feet one inch tall affect his life? Do you think that extremely short stature constitutes a significant hardship for men 5'2" and...

Hey, Well the summer is coming up, and as usual I do not have a lot planned really, other than a few days in Switzerland, and my sporting commitments. I am located in the UK, and I am looking for a short course that can be done online in Physics (I would have completed my AS levels). I do...

I've managed to calculate the viscosity of glycerol to be about 1.9 P. Google says it's supposed to be 1.5. Could I say that evaporated water has caused the glycerol to become more viscous than it should be? (It could just be a thicker glycerol but I'm just looking things to blab on about)...

Homework Statement Pb(NO3)2(aq) + H2SO4(aq) → PbSO3(s) + HNO3(aq) Pb + (NO3)2(aq) + H2 + SO4(aq) → PbSO3(s) + H + NO3(aq) The Attempt at a Solution So far I've done that, and now I'm stuck I see h2 and h can I cross out both or do i have to balance right now? My teacher said you can...

[SOLVED] Short optics question Shiny lawn spheres placed on pedestals are convex mirrors. One such sphere has a diameter of 42 cm. A 13 cm robin sits in a tree 2.1 m from the sphere. (a) Where is the image of the robin? in cm b) How long is the robin's image? in cm1/f=1/do+1/di hi/ho=-di/do Ok...

Homework Statement this is a 2 marks question a hole is drilled through a piece of steel what happens to the diameter of the hole as the steel is heated Homework Equations The Attempt at a Solution i guess the diameter of the hole decreases as both the outer as well as...

hi everyone, I am having a tough time convincing myself about the virtual short concept in opamps, As i understand from texts, on the application of a voltage on one of the input terminals of opamp, the voltage at the other input terminal is also forced to match the voltage on the first...

What is there about a particular protocol that defines its range of use? Is there such definition? i.e. 802.11 is used for short range high bandwidth, GSM/EGPRS for long range cellular communications and bluetooth for even shorter range communication on PANs. Is it possible for 802.11 to be...

What happens to gravity when something is very very dense but not a black hole? Do parts of it still attract each other as in less dense objects, ie according to the same inverse square law?

I have a few questions concerning opamps. First what is the big deal about infinite common mode rejection? It seems to me by looking at the open-loop gain equation A(V2 – V1) = V0 it is obvious that when V2 = V1 the output is zero (common mode rejection). This may be where I am confused …...

A Boeing 777 crashed yesterday at Heathrow apparently due to engine failure http://uk.reuters.com/article/domesticNews/idUKHO86894720080119?pageNumber=1&virtualBrandChannel=0 In the event of catastrophic engine failure wouldn't it be normal for Boeing to issue instructions for safety checks...

I notice consistently in the aftermarket exhaust world that in the majority of cases, when a longtube is placed on an engine the low to mid-range power picks up. This is also with the same size diameter primaries but different lengths. So I am comparing: Long tube: 30" primary tubes...

Amidst the trees and their canopy, a green hued kaleidoscope, lies a hidden meadow in spring, a retreat from the shadows, where the sky meets the earth. The sun sojourns there, sending gentle winds to dance with the young grasses. They sway to and fro, an auditorium of slender green children...

Homework Statement Hi, This isn't so much an actual problem, just more of a general question. Can anyone give me a layman's explanation of what a short circuit is and how a circuit breaker deals with that? Or, can anyone refer me to any sources that can? I have taken high school physics...

Is there any Short circuit protection diagram designed for power supplies which the current doesn't drop below 1A? Can you show me any?