Formation Definition and 480 Threads

Hello, I am looking for a model of galactic star formation that I can study. Particularly, I would like one that works well for mature galaxies like the Milky Way. It also should be relatively recent as well. I am primarily interested in the yearly rate of star formation for galaxies like the...

I am doing a project in Chemistry and I need to use Hess' Law to cancel two equations and if in one equation the NH4NO3 is solid and in the second one the NH4NO3 is aqueous. The equations are: 1: NH4NO3 (s) + HCl (aq) --> HNO3 (aq) + NH4Cl (aq) 2: NH4OH (s) + HNO3 (aq) --> H2O (l) + NH4NO3...

I recall watching a program on TV that said the Yosemite Valley was formed by graben as opposed to being carved out by a glacier. I wanted to look into it further, but haven't been able to find anything in the first several pages of Professor Google's archives. Is anyone familiar with this, or...

Homework Statement An object 4.29 cm high is projected onto a screen using a converging lens with a focal length of 32 cm. The image on the screen is 51.7 cm. Where are the lens and the object located relative to the screen? ho=4.29 cm hi=51.7 cm ƒ=32 cm Homework Equations 1...

How should I place three objects for e.g three pencils so that no shadow is formed for them throughout the day(light source:sunlight to be considered)??

Would you expect to find stars being made more easily in a cool, high-dense nebula or conversely a hot, high-dense nebula? Looking at for example the pillars of creation which is a stellar nursery, but what would be classified as hot and cold? relatively speaking. thoughts? thanks pf!

i think i don't understand the nature of "Binding Energy" very well, and i have a very significant question what iam really intersted in; is the nuclear binding energy, but i think (hopefuly iam right) that it has the same physical nature (NOT origin) as atomic and molecular binding energies...

Hi, does anyone know how much of the universes's iron or carbon has been made in supernovae that formed black holes? Is it 5, 10, 50 % of the iron currently pressent here? And, if se, do we have any idea how much of the average stars content gets traped in the BH versus the mass of the...

Homework Statement Consider a simplified model of cloud formation. Hot air in contact with the earth’s surface contains water vapor. This air rises convectively till the water vapor content reaches its saturation pressure. When this happens, the water vapor starts condensing and droplets are...

Homework Statement If α is an arbitrary constant and a a fixed constant show that xcos α + ysin α = a is the complete primitive of the equation (y - xdy/dx)^2 = a^2( 1 + (dy/dx)^2) Homework Equations The Attempt at a Solution FIrst I found the first derivative by...

Hello all, I'm in gen chem 2 and we're going over how to calculate the enthalpy of lattice formation. The way given is to use the Born-Haber process and add the enthalpies of all the steps in between. e.g. Na_{(s)} --> Na^+_{(g)} + e^- (388kJ) There are three or four of these, and we combine...

I was studying Density functional theory, the premise of whose reasoning needs one to accept the phenomenon that when we place electrons into a potential, they "arrange" themselves into an unique wave function/charge density. Are there any forces that oppose this arrangement? (other than the...

So I wasn't sure if this is the most appropriate place, but recently I got cut on my palm. So its been about two days, for which time I have been using a bandage to conceal the cut. (Note, the cut isn't large, surface area ≈ 1 square cm (probably slight less) However, i noticed the formation...

Homework Statement Not really much of a problem - just a general question and some speculation on its answer. Why do some ionic compounds such as aluminum fluoride form hydrates while other ionic compounds such as sodium fluoride don't form hydrates upon being dissolved in solution...

Homework Statement Why does an image form when light rays meet in ray optics? Is there explanation to it? Homework Equations The Attempt at a Solution I thought of an explanation myself and thought that it cannot be explained just like many other things cannot be explained like...

It seems to me that the heat of reaction nullifies the concept of the heat of formation. The heat of formation is the enthalpy change associated with formation of 1 mole of a compound from its constituent elements in its standard state. The heat of reaction is the enthalpy change that occur...

Hi... During mitosis there is formation for spindle fibers in Prophase.My question is how these fibers are made and what proteins are included in forming it?

Hello everybody, I'm new here and i have a question about the activity of our galaxy's Supermassive Black Hole. Did it influence the star-formation activity or was it vice versa? I would be grateful if someone could tell me anything about this or give me some information directions. Thank you.

I write this in the hope that somebody reading this can explain to me, a laymen, in non-mathematical, plain English terms, why my thinking is wrong regarding the calculation of the age of the observable Universe and the formation of the elements in the Periodic Table given the (short) age of...

Homework Statement NH3 + O2 --> NO + H2O Enthalpies of formation NO: 91.3 kJ H2O: -241.8 kJ NH3: -45.9 kJ Homework Equations delta h = sum*moles enthalpy of formation of products - sum*moles enthalpy of formation of reactants The Attempt at a Solution = [(1)(91.3) +...

Good day, I was recently asked to look into the process of thermal annealing of thin metal films in order to induce nanoparticle formation. However, I have been terribly unsuccessful in finding any sources that describe exactly how this works. I understand the basic idea of thermal annealing...

Confusion over the formation of cooper pairs Hi all, There are 2 points I do not get: 1. I read something saying that phonon is an energy packet of "heat and sound", and propagates through lattice vibration...so, I thought it is saying that phonon is emitted by one electron, then...

Currently using resources like: http://www.matterandinteractions.org/Content/Articles/circuit.pdf http://www.phy-astr.gsu.edu/cymbalyuk/Lecture16.pdf I don't seem to understand why the surface charge densities shown in the pictures are stable. I understand that the densities shown create...

Homework Statement I am to create "my own" protein that follows the primary structure, then can be formed to follow the secondary structure, and so on until of course the quaternary structure. I am looking for some help on creating my protein so that it meets these needs (first follows the...

This is what I understand. I can be wrong though. Please let me my conceptions are wrong. If by ''space'', you mean ''distance between two objects'' then the answer should be ''yes.'' Because since the distance between two distant objects in the universe is actually increasing, it should mean...

When we dip a wire ring in a soap solution and then take it out, why does it form a soap film inside? Is there any explanation behind it?

I understand how conservation of momentum leads to planet formation and planet rotation. However, after studying this model, I have ran into a point of confusion that I cannot find the answer to: Why don't the planets collapse into the sun just as dust particles collapsed inward via...

Hello! At work we have an UV aging test chamber that produces around 140 W.m^-2 UVA 15 W.m^-2 UVB and less then 1 W.m^-2 of UVC. The chamber is big, we have to go in and out to collect the items. Is it possible to have ozone formation or other harmful gases inside the chamber?

Consider NH3, if it forms a dative bond with an H+ to form an ammonium ion, will the oxidation number of N change from +3 to +5? My reasoning is that it uses 5 electrons in bonding. Is that correct?

Hi! I have two questions: 1) I'm a little confused about image formation. Suppose there's an illuminated object place in front of a mirror. The object has a rough surface causing a diffuse reflection so when lights hits the object, the rays will be scattered all around the room. Now the...

Hello physicsforum, As the topic name says, I would like to know if a photon forming electron-positron pairs spontaneously could or does affect it's speed. Correct me if I'm wrong, but photons do form these pairs (and heavier?) even without the correct amount of energy, right? And if they do...

Regarding the creation of the universe and the current model: Is it assumed that the universe, at the time of creation was finite in size (or at least more finite than it is now) prior to the rapid expansion, or was the protoexistance finite in size in an infinite universe? So, did the...

Homework Statement I'm doing physics and I don't know if this counts as physics or Chemistry (sorry if this does not belong here) Homework Equations \Delta H = \Delta U + P \Delta V \Delta U = Q + W The Attempt at a Solution So firstly I started off with ## \Delta H = \Delta U + P \Delta...

Homework Statement Using the information provided for energy changes associated with the formation of carbon dioxide, calculate the enthalpy for the formation of carbon monoxide. C(gr) + O2(g) → CO2(g) ΔH (-393.5 kJ mol-1) CO(g) + ½ O2 (g) → CO2 (g) ΔH (-283 kJ mol -1) C(gr) + ½ O2 (g)...

what happens to the gluon linking Quarks at time of formation of quark star? whether the quark star consists of only quarks or quark gluon plasma?

This scenario is described by Lenard Susskind in a lecture on general relativity starting at time stamp 44:23 in the following video. The scenario is that a spherical shell of radiation is directed inward to a point. The shell contains enough energy to form a black hole. He states that...

When a (say 50 meters) asteroid 'A' strikes a larger (say 500 meters) ‘equally hard’ asteroid 'B' at a small angle to the asteroid 'B' would have two vectors, one large vector parallel to the asteroid 'B', another second small vector perpendicular to the asteroid 'B'. ...

Homework Statement Compute the mass of volatile material (specifically just H and He) not accreted by the Earth. Assume the mass accreted by the Earth is 7e23 kg. How does the mass of the missing volatiles compare with the actual mass of the Earth? Use the following table: Principal...

Hi, The standard enthalpy of formation of carbon gas or C(g) is the enthalpy change for the formation of 1 mole of carbon gas from its elements in their reference form which for carbon (I believe) is C(graphite). Now I find the following standard enthalpy of formation for carbon gas / C(g)...

I've heard that, when a soap bubble is given a charge, it expands. I was just wandering whether, when you wet a ring made of metal with a soap solution and blow to it slowly, the bubble created expands because of theat above principle. Does The friction between the metal ring and the bubble...

Hi, This is my first post and first of all I would like to thank all the contributors to this forum for the amazing amount of information provided here. I’m not a physicist, but I like physics (although I have only a qualitative understanding of it) and I like to smash my brain on difficult and...

Can we see a real image with our naked eye without using a screen to capture image? Also, we all know that virtual image formation in a concave mirror will be always erect. Check out the image below. Spoon here acts as a concave mirror and the image is inverted. Why is it virtual then?

Hi, I have a question regarding the following picture of a lattice of ice: Why does it form the shape that it does? Is it because of the repulsion of charges from the valence electrons? Thanks,

Homework Statement Use the method of cylindrical shells to find the volume generated by rotating the region bounded by the curves about the specified axis. y=x^4, y=0, x=1; about x=2 2. The attempt at a solution I know how to do the problem, except how to find the radius. Like I know...

Hi there, I have to solve this problem: Use the following data to estimate the molarity of a saturated aqueous solution of ##Sr(IO_3)_2## So, I think I should use the Van't Hoff equation in some way, but I don't know how. I also have: ##\Delta_r G=\Delta G^o+RT\ln K## ##K## is the...

Hi there: When using ΔG=ΔG°+RT ln Q to calculate the energy yield of a reaction, does it matter if I use ΔG° calculated at 1°C or 25°C? Also, why are there two choices and when are they each applicable? Finally, I have also seen ΔG°' written (note the prime). What does this mean and how does...

In astronomical telescopes, they use a convex mirror to from a real image, which is formed at the focus of the eyepiece lens, effectively forming an image at infinity. But how can it truly be at infinity? If it was truly at infinity then how could you see it? Also they say that image at infinity...

came across the concept of Frame dragging. i cannot find if this phenomena also aids in addition to the conversation of angular momentum the formation of an accretion disk around neutron stars/black holes. cheers

Here's a question from my textbook: "Why do you not see a spectrum of colors when light passes through a flat pane of glass?" However I think that a spectrum of colors will be formed when light passes through a flat pane of glass. The colors will all be parallel to one another, unlike a prism...

Homework Statement 50.0 mL sample of 2.0 10–4 M CuNO3 is added to 50.0 mL of 4.0 M NaCN. The formation constant of the complex ion Cu(CN)3 is 1.0 10^9. What is the copper(I) ion concentration in this system at equilibrium? The Attempt at a Solution I did a dilution and got the new...