Lead Definition and 292 Threads

One of the foundations of General Relativity is diffeomorphism invariance - the fact that the laws of physics are invariant under smooth coordinate transformations, and thus the laws must involve tensors. My question is, why doesn't this imply scale invariance; after all, isn't a change of...

Here are some questions that have been puzzling me about symmetry and charge. Any answers to any of these questions would be very helpful. Thank you. What does U(1) gauge symmetry mean? Does anyone have a simple explanation? Can Maxwell's equations be derived from the premise of U(1)...

Homework Statement A 5cm long, 30g lead bullet strikes a wall at 27°C and melts on the wall without splatter. How fast was it going? What is the force on the wall? If the wall is made of 1kg of marble, what temperature will it reach? Homework Equations I don't know how to find the...

Suppose you are at a point (x0,y0) in space. There is a planet at position (x1,y1) orbiting in a circle a distance r away from the orbit center (x2,y2). The planet has constant angular velocity as it orbits. You move at a constant speed towards the planet, and want to move in a straight line...

Hi, I have decided to increase inlet T and P of a typical diesel engine (operatiing on dual air standard cycle). THeoretically if all other parameters r same, I have observed that t2 (temp at the end of compression) and p2 increases, but t3 (temp at the end of constant volume heating) and...

Hello, I am willing to do some experiments with molten Lead Fluoride and Crayolite in an electric muffle furnace, but I am not sure what type of crucible to use? Platinum Crucibles are way too expensive and I am assuming Alumina Crucible is not suitable... so, are there any other...

Homework Statement A flat, uniform cylinder of lead floats in mercury at 0 degrees Celsius. Will the lead float higher or lower then the mercury temperature is raised? Homework Equations None. The Attempt at a Solution Since the mercury is heated, then the density will be lower...

True or False: "The moon has no atmosphere because we never see any clouds on the moon." Apparently, "The moon has no atmosphere because we never see any clouds" and "We never see any clouds on the moon because it has no atmosphere" are logically equivalent statements to the layman...

According to theory of black hole radiation, black holes are expected to emit a thermal spectrum of radiation, and thereby loss mass, owing to the E=mc2 equation. Well, everything was clear to me till I got to the last point. why should there be loss only in mass?? couldn't the mass be same and...

How many atoms are in one mole of the element Lead(Pb) -Intrepid Elder

Had our observations shown shown that the Universe was not expanding, and was instead static, where would that have lead us as far as Cosmology is concerned?

I am offered Sealed Lead acid batteries at heavy discount (half the price) at local Sale. But they were manufactured some 5 years back. How much damage does long storage do to them? They have never been touched. Just bought 5 years back, and stored.

We discussed this manner in terms of inductor, not so long ago. I fully understood from many posts provided why does it lag. I mean, not everything can be fully understood but I got a good intuition about it. Question arose not so long ago, and I couldn't find anything good on the...

lead battery(rechargeable)...? i was just wondering that the common lead batteries (the ones used in cars) supply us AC or DC? i saw a battery attached to a UPS and it steps up the 12V to 240V. so what i concluded was that it must give us AC. but how does it supply AC? i mean its positive and...

Can someone calculate the weight of the object and what would most likely happen in the following experiment that I have always been curious about: Imagine you have a brand new 52-foot standard refrigerated cargo trailer mounted on a brand new standard heavy duty sleep cab tractor (i.e., an...

Here is the process: For example, take 28. Its prime factors (taken with multiplicity) are 2, 2, and 7. The sum of these is 11. Double it and you get 22. So, the sum of prime factors of 28 multiplied by 2 is 22. Repeat this process until you reach a loop or a stable number. For 28, if you...

I want to charge a led-acid battery it needs 12V DC 1.i have transformer to convert 220V AC to 12V AC after that can i give 12V AC to bridge rectifier and from bridge rectifier to battery terminals directly or should i use a filter to remove the fluctuations in DC ? 2. what should be the...

I have a cordless electric lawnmower that runs on sealed lead acid batteries. It is on it's second battery, which has noticeable degraded performance and will need replacing soon. My question is why the original battery, which was rated at 17 Amp-hours, lasted twice as long as this second...

Homework Statement Homework Equations use clausius-clapeyron equation: \frac{dp}{dt} = \frac{L}{T(V_{2}-V_{1})} which can be rearranged (i think) in the following: p = p_{0}+\frac{L}{\Delta V}ln(\frac{T}{T_{0}}) The Attempt at a Solution so using the above equation i solved...

Hey guys and girls The first thing I should probably ask is why do fuels (Hydrocarbons) spontaneously ignite when they are compressed, this seems rather strange to my brain in fact it makes my brain feel like it's having a meltdown (if you have ever had that feeling). The whole idea confuses...

Sorry about the intrusion as I really don't belong here as I have absolutely no background in physics but I have a couple of questions regarding lead acid batteries that I have been unable to find answers to on the internet. First question - why does a battery spark/arc when the negative is...

I hope so. Teen who challenged Bachmann to Constitution showdown is running for class president http://news.yahoo.com/s/yblog_thelookout/20110516/ts_yblog_thelookout/teen-who-challenged-bachmann-to-constitution-showdown-is-running-for-class-president There is hope for this country. We...

What do you think about this? Are all these uprisings a sign that Muslims are ready for self-determination and will finally enter the world stage, or is this just an opportunity for the next round of corrupt politicians and dictators to grab power? Is democracy even possible in the Muslim world...

Homework Statement a 500 g lead mass is heated to 150 C and placed on a block of ice at -10 C. how much ice, if any will melt? 52 kg = block of ice Homework Equations The Attempt at a Solution i didint know where to start so i did qmcdeltaT + qmcdeltaT = 0, and i failed at it i...

Homework Statement An a particle of mass 6.6 x 10-27 kg came closest to an atom of lead with a distance of 4.8 x 10-14 m. At what velocity will the a particle rebound directly away if the collision is totally elastic? Mass of the Alpha Particle - 6.6 x 10^-27 kg Alpha particles are...

As title suggest. Thanks :smile:

How does the electromagnetic gauge field lead to charge superselection and why does this fail when the symmetry is broken as e.g. in superconductors?

A lead rod and a common glass rod both have the same length when at 21.0° C. The lead rod is heated to 50.0° C. To what temperature must the glass rod be heated so that they are again at the same length? I did this: L = a*L0*T a (thermal expansion) of lead = (29e-6) a (thermal expansion) of...

Homework Statement A lead bullet at 320K is stopped by a sheet of steel so that it reaches its melting point of 600K and completely melts If 80% of the k.e of the bullet is converted into internal energy calculate the speed with which the bullet hits the stee sheet. Homework Equations...

Homework Statement The nucleus of a lead atom has a charge of 82 protons a. what are the direction and magnitude of the electric field at 1.0x10^-10 m from the nucleus? Homework Equations E=Kq/r^2The Attempt at a Solution I did E= ((9 x10^9)(1.6X10^-19)^82)/ (1.0x10^-10)^2 but when I...

Homework Statement Let f be continuous at c and f(c)>0. Prove that there is an open interval (a,b) centered at c such that f(x)>0 for all x that are elements of (a,b) Homework Equations we are supposed to use the sign preserving property?? The Attempt at a Solution I tried...

Homework Statement When lead is melted at atmospheric pressure the melting point is 327.0 degrees C, the density decreases from 1.101 x 10^4 to 1.065 x 10^4 kg/m^3 and the latent heat is 24.5 kJ/kg. Estimate the melting point of lead at a pressure of 100 atm. Homework Equations...

Hi everyone, I would please like some suggestions regarding where my error is, designing a lead compensator with the root locus method for a unity feedback control system where G = [12.5] / [2.5 1 2500]. I want to set the overshoot zeta = 0.5 for an overshoot of 16%, and settling time Ts =...

Hello everyone, Ok generally what do they mean when they say vasodilation in periphery lead to reduction in blood pressure? Do I have to think of this as expanding the size of a fluid filled container so less fluid splashes againts the walls reducing pressure. Or do I have to think of this...

Hi I am new to the design game as it where and I have scoured books and the internet looking for calcs, examples, help with a design I am putting together which involves raising and lowering a heavy object using a lead screw. I know its not strictly CNC stuff but I believe someone may be able...

Hi all, anybody knows why x-ray cannot penetrate into a sheet of lead paper deeply? Do only the big amount of electrons in lead atoms diffract the x-ray, or the protons in the atoms also contribute the diffraction ? Thank you for your time!

What's ground lead screws ? What's the differences between the ground lead screws and lead screws ?

Homework Statement Why is it harder to start a battery in winter rather then summer? Homework Equations Nerst Equation Ecell = Ecell - RT/zf(lnQ) The Attempt at a Solution Isn't the lead sulfate bettery unique such that the electroyte for the anode and cathode is the same...

Hi, firstly apologies for what might seem like a 'basic' question, but I've been trying to work this out for a while. I have a sealed lead acid (SLA) battery - 6V 4AH. I would like to use this battery to power a 4V coil (for a display) - that is capable of (potentially) drawing the full...

My set up was simply putting two lead plates into a beaker of sulphuric acid, then connect the lead plates to a power supply. What is the reaction for charging and discharging the cell? All equations I could found contain lead (IV) oxide... Is the reactions of my set up differ from a real...

Homework Statement A 5 g lead bullet moving at 343 m/s is stopped in a block of wood. All of the kinetic energy goes into heat energy added to the bullet. The initial temperature of the bullet is 24 degrees C. What is the final temperature of the bullet in degrees C? (cPb = 0.128 kJ/kg . K...

1. Predict the minumum speed of a 20.0MeV proton as it passes within 1.0x10^-13 meters of a lead nucleus having 82 protons. (Note: 1eV = 1.6x10^-19 Joules) 2. How do I start off? 3. All i can think of is to get a charge for the lead nucleus by using q=ne which is the number of...

Homework Statement A clock is placed on a floor covered with lead density \rho and thickness d. Use dimensional analysis to show that increase in gravitational field strength at the clock dueo to the layer of lead is proportional to Gd\rhoHomework Equations The Attempt at a Solution to show...

Hi, I am having difficulty understanding how to convert pole and zero locations of a lead lag compensator into lead and lag time and vise versa. I have a digital lead and lag compensator which requests: gain, lead time (min) and lag time (min). However i have the gain zeros and poles of...

Moving Target Lead Time ?? I am new to the forum...so I thought I would start with a simple question.. How do you figure up the lead time on a moving target Example 1.Target is moving from right to left @ 3.0 fps 2.Target is @ 60 ft out 3. Projectile is shot @ target @ 100...

Jewelry for kids! Guess where it was made? http://www.nytimes.com/aponline/2010/01/29/health/AP-US-Cadmium-Jewelry.html

Homework Statement If you pour 0.50 kg of molten lead at 328°C into 2.5 liters of water at 20°C, what will be the final temperatures of the water and the lead? The specific heat of (solid) lead has an average value of 3.4 X 10-2 kcal/kg • °C over the relevant temperature range.Homework...

Homework Statement Calculate the half life for alpha decay of ^{208}_{82}Pb (in years) Homework Equations gamow factor transmission probability coloumb potential The Attempt at a Solution...

A sound wave can be interpreted in any of four ways. Two of those involve the correspondence between (1)displacement and position and (2)pressure and position. [By "position" here I refer to the distance from the source. Positive refers to going away from the source.] These waves are 90...

Homework Statement A girl wishes to make a lead casting of an object which will require 2kg of melted lead. if the lead was stored in her basement at approximately 55 degrees F, and it is melted to a 1/4" thick steel pot of approximate cross sectional area of 12in^2, how long will it take...