Lead Definition and 282 Threads

I heard that many industries use lead for shielding harmful radiation. do you know why?

For a 3rd order system, can I use 2nd order approximation (granted dominant pole is ≈5 Tau away from third pole), when designing a Lead or Lag compensator? Can this OLTF = K/{s(0.1s+1)(s+1)} be approximated to 10K/{s(s+1) which ultimately gives CLTF=10K/{s(s+1)+ K} ? and then design...

I mean I don't see any theory actually derives gravitational interaction from actual fields of particles. I only see some manipulation of GR to make it look like a quantum field theory. So are these theories looked upon as one more step to actual unification or are they the FINAL unification...

Homework Statement Question 2. Tetraethyl lead was used in early model cars to help reduce engine knocking, boost octane ratings, and help with wear and tear on valveseats within the motor. In Australia, our petrol contained lead between approximately 1950 and 2002. Consider the impact of...

I know lead is a great shield against gamma particles due to its extraordinary density, but I wonder if it can also block beta particles, or is it transparent to them due to being electrically conductive? Thanks ahead of time for your responses!

Hi I'm trying to make a lead screw in Creo which would be used to move a 400lb load linearly along the ground. This would be turned manually using a lever as shown in the pic (not the complete model). I have used a lead screw with a major diameter of 1 1/4 and determined the torque to move...

Hello, Out of curiosity, can MOOCs lead to getting accepted into a graduate school? I'm interested in knowing under what conditions (if any) MOOCs lead to graduate school. Thank you for your responses in advance.

Hi all I understand that at high frequencies, a twin lead Tx line has high radiation losses because the conductor separation becomes close to the wavelength size, allowing the conductors to act as antennas. Can one still be used to transfer a high frequency signal a short distance from an...

Homework Statement Learning about lead-lead dating to determine the age of things (specifically the solar system using meteorites)... I can't seem to understand what the meaning of "common lead" is. So far the best I'm getting is that it is some sort of contaminant. What is the...

Lead Acid Battery "Internal Resistance" and Temperature Hello, I've reached my wit's end trying to understand the theory behind charging lead-acid batteries. I believe I have read over twenty different articles, maybe six hours worth of studying. According to what I've read: Charging...

How can I perform this integral \begin{equation} \int^∞_a dq \frac{1}{(q+b)} (q^2-a^2)^n (q-c)^n ? \end{equation} all parameters are positive (a, b, and c) and n>0. I tried using Mathemtica..but it doesn't work! if we set b to zero, above integral leads to the hypergeometric...

Problem: The temperature of a piece of lead is increased from 20C to 35C while its volume is held constant by increasing the hydrostatic pressure. If the initial pressure is 1atm, what is the final pressure? Honestly, I'm not sure where to begin here. Everything we have done thus far has...

**EDIT** Never mind just realized that it is lead(II) in PbI2. Hehe... Awkward Why does lead iodide have the formula PbI2? Pb needs to lose (or gain) 4 electrons to have a stable octet and Iodine needs to gain only 1. So why isn't the equation PbI4? It seems like it should be... Please...

In a truly technologically advanced society everything is available to all for little money. If such a thing does not happen then there is no technological progress. In 1983 the Motorola DynaTAC 8000X cell phone was 4k and as heavy as a brick. The battery only lasted a 1/2 hr. Nowadays...

Can anyone explain why a positron, in a charged magnetic field, is able to go through a 6mm lead plate, as seen in Anderson's positron experiment? Initially I thought that it could be quite similar to the gold foil experiments, but one of the features of the gold foil experiments is that it...

I know this might sound like a very, very peculiar question, with a very, very peculiar description. Anyway, I am currently going for the fourth and last year of my curriculum in Physics school and I want to be completely honest with you before I even ask: I do have a noticeable bunch of courses...

About 6 years ago, I made a precipitate of Lead Iodide in water by mixing Potassium Iodide and Lead Nitrate. I have kept the precipitate in a test tube. Would anybody know how stable is the precipitate over time. The temperature has been mostly between 20 and 32 degrees depending on the...

At 110Kev they block above 90 percent but I wonder about other lower frequencies specifically microwaves and radio waves?

is this correct? mass attenuation coeff. = 8.636 cm^2/g 8.636 * (density of lead: 11.3 g/cm^3) = 975.868 per cm thickness (mm): t= 9.21 / 975.868 = 0.009 cm = 0.09 mm

In an experiment a test tube consisted of 2 layers. Bottom one was organic (chloroform) and top was KI (potassium iodide) . We added Pb02 to it and was told that it was not going to be soluble. Then we were supposed to observe the organic layer for something to happen. (Hint: The color of...

Hi, I try to prove, that function f_n = \frac{\sin{nx}}{\pi x} converges to dirac delta distribution (in the meaning of distributions sure). On our course we postulated lemma, that guarantee us this if f_n satisfy some conditions. So I need to show, that \lim_{n\rightarrow...

Considering the vibrational damping of bubble wrap. My basic premise is that there are three main contributors to the damping effect: 1) Surface tension of the sheet structure and the bubbles themselves when subject to applied force causes dissipation of force away from applied direction 2) The...

A sine wave traveling in [SIZE="4"]+x direction can be represented by \cos(\omega {t}- kx+\phi). As shown in the drawing attached where \phi=\frac{\pi}{2}: [SIZE="4"]a) Is a plot that holds t=0 and two waves along +x direction. t=0\Rightarrow\; \cos(\omega {t}- kx+\phi)\;=\;\cos(-...

Hi everyone, I don't mean to offend anyone (actually I'm looking for help), it's just that I am having a hard time believing the superposition principle and below is the reason why I cannot believe it and what I want to do because of it. so I was reading chapter 21 on my physics book and...

On the flat bottom of an aquarium is an old fashioned balance. On one scale of the balance is a piece of plumbum, on the other side is a piece of iron. The scales are exactly in balance. Now we let the aquarium fill slowly with water, until the entire balance is under water. What happens now...

I'm surprised this hasn't been discussed more. Essentially we have a situation of increasingly aggressive behavior on the part of China in both the East and South China Seas. This to me looks a lot like turn of the 20th century Europe and we have another Wilhelmite Germany on our hands. So the...

Hi all, I have a question that seems very simple but I just do not see it;) Let α denote an r×1 vector with arbitrary entries; I'm trying to construct an 1×r vector m such that αm = I, where I is the r×r identity matrix... The first question is: is this possible? I tried the...

I am trying to find the amount of ice that melts when a lead bullet traveling at 240 m/s at 30 °C. This textbook claims I should use the formula \dfrac{1}{2} m v^2 + m_{bullet} c_{bullet} \left|\Delta \right| T = L_f \Delta m What I don't understand is why I shouldn't first calculate how...

why does this integral: double integral (x+y) dA , A is the area bounded by the triangle with vertices (0,0) (0,1) (1,0) equal 1/3 While this one, (x-y) dA , A is the area bounded by the same vertices equal 0? (not looking for the math, already worked them out, just looking for some...

Entropy of molten lead "freezing" Lead melts at 327.5 C.° The latent heat of melting of lead is 24.1 J/g, and the heat capacity of solid lead is 0.14 J/g °C. You take 100 grams of molten lead at a temperature of 327.5 C° and pour it on the sidewalk. The lead freezes and then comes into thermal...

Homework Statement Determine the number of K electrons ejected from a foil of lead with thickness 0.5 x 10^20 atoms/cm^2. It is bombarded by 10^4 photons that each have an energy of 88keV. Homework Equations From a figure in the book, it shows that u/p (7.483 cm^2/g = .7483 m^2/kg). I...

Anyone knows what is the approx. internal resistance of a lead battery, say, 12V, 20Ah. Thanks

Homework Statement Today In class(1st day of physics) the teacher paired us up and told us to figure out how to make a lead ball float in water. The ball has a radius of 1 meter and is made of lead. To make it float we can hollow it out and fill the empty space with air. For this problem we...

So, I really like my biology classes. It's cool to learn things about biological systems that I can apply towards ideas of medicine. Biology encapsulates so many finds. I really like the courses but I also want a secure income down the road that will lead to an interesting career(Why I passed...

I have a puzzling question that a gentleman discussed and have differnt view on the problem, the probelm goes as follows: What is know is the Resultant of a Vector Addition, the goal is to find the two vectors from which the resultant came from. The other piece of information that is know is...

Newb Questions -- One lead outputs from schematics? Hey there PF, I just recently got into electrical engineering and created a voltage controlled oscillator and control voltage keyboard to go with it(the goal is a modular synthesizer). I've visited quite a few sites and learned a lot so far...

What do you think? http://www.aftenbladet.no/energi/aenergy/Britain-aims-to-lead-on-nuclear-energy-2989235.html

I have had a question that I cannot get an answer for. I recently had an exam for energy in the nucleus which included a question about why lead nuclei would be inadequate for use as a moderator in a reactor. When I got the answer for the question, it stated that the lead nuclei reflect neutrons...

Hi, I have simple question: In small OFF GRID wind turbine systems, it is worth to continuously charge & discharge 12V Lead Acid Batteries? this means that we want that our loads (lights, Fans e.t.c) are 24hours taking power from wind turbine & batteries will continuously charge &...

Hi guys, Was trying out a home made double slit experiment as I've seen on youtube with a laser pointer and 2 pieces of pencil lead. Then I realized that I can obtain the same interference pattern with the single pencil lead. Is this equivalent to a double slit interference?

Why does inflation mean that the universe was much smaller at 380000 years after the big bang than we would predict from the Big Bang model alone? What would we expect the two sizes to be?

There is a spherical lead ball with a spherical cavity. It is heated. The size of the cavity increases. Why does it do so? Also, does it matter what happens to the cavity if it is not present at the centre, but rather a little removed from the centre? Will it remain spherical?

Not sure if this is the right forum, but I'm an electrical engineer studying controls so here goes. Here's my background on what I know. Lead or lag compensators generally have the form C(s) = K*(s+z)/(s+p), i.e. the controller has a DC gain and introduces a pole-zero pair. In the case of a...

Actually i am using lead screw drive by motor along with rope drive. If you will see the attachment, yuo can clearly understand the working principle. In this working priniciple, when we used to start the motor, carriage power use to go up through lead screw drive.Rope is connected to this...

Homework Statement A container in the form of a rectangular prism measuring 2m by 3m by 4m is covered with a layer of lead shielding of uniform thickness. Model the volume of the shielding as a function of its thickness. Treat the shelding as a hollow rectangular prism. DO NOT SIMPLIFY...

Steve Carlip says this [back in 2007], here,: http://www.2physics.com/2007/06/symmetries-horizons-and-black-hole.html"...Until fairly recently, no one had a clear idea of the microscopic states responsible for black hole entropy. Today, we suffer the opposite problem: we have many...

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...