Density Definition and 1000 Threads

Here is the problem link picture http://i.imgur.com/0BtcXJk.png I know that omega=density/critical density so I know I can find the value of all of those. DE is dark energy and M is matter (I'm pretty sure). I assume I have to sub that formula into equation 1, and then rearrange it to create a...

Homework Statement find μ and σ^2 for the following probability density f(x) = x for 0<x<1 f(x) = 2-x for 1 <= x < 2 f(x) = 0 elsewhere Homework Equations μ = ∫xf(x)dx σ^2 = ∫x^2 f(x)dx - μ^2 The Attempt at a Solution first we find the mean. we split up the integral into sums of different...

Homework Statement If the distribution function of a random variable is given by F(x) = 1- 1/x^2 for x>1 and F(x) = 0 for x <= 1 find the probabilities that this random variable will take on a value a) less than 3 b) between 4 and 5The Attempt at a Solution since they use the capital F i...

Hello I have question about universe density so is there any equation what says how to calculate universe density because on meany cosmology equations:wink:.

Homework Statement An air-filled capacitor is formed from two long conducting cylindrical shells that are coaxial and have radii of 48 mm and 72 mm. The electric potential of the inner conductor with respect to the outer conductor is -536 V (k = 1/4πε0 = 8.99 × 109 N · m2/C2) The average energy...

Hello to everyone. My first question on this forum (it was quite tricky thinking of a heading and prefix for this thread!): Imagine for a moment that there is a hot air balloon which has a strong shell forming the balloons shape rather than one made from material and it weighs the same as a...

Homework Statement This is a wire whose shape is given by y = acos(x/L). This wire has a linear charge density of +λ, and is it desired to determine the electric field at the point (0,y) where y > a. a) If a=0, determine the amount of charge the wire has. b)If a > 0, is the total charge on...

Homework Statement At what rate would stars have to be producing light (how many photons per second per solar mass start) in order for the energy density of photons in the universe be constant? Assume current values of cosmological parameters. Do it for current time. Homework Equations e =...

Homework Statement If the energy density of the vacuum were the value 10^133 eV/m^3 , what would the value of the Hubble lookback time be for such a universe with no curvature and no other matter? Homework Equations Possible equation... ...Lookback time = ln(1+z)/H The Attempt at a Solution...

Homework Statement Basically I'm given a feed flowrate - 70,000 gal/day I know the weight percent is 35% and the component is Triethylene Glycol - density - 1.255g/ml Homework EquationsThe Attempt at a Solution So i did this 70,000 gal/day * .35 * (.0378mL/1gal)* 1.255g/mL = g of Triethylene...

Homework Statement Convert 1 ##Gev## to Kelvin, and convert ##GeV^{-1}## to meters, seconds, and convert ##GeV^4## to density ##(kg/ m^3).## Homework Equations natural units ##c=h=k_B=1## The Attempt at a Solution I know to convert energy to meters, I can use ##\lambda =hc/E##, I get the...

I recently bought a 1-pound .999 fine copper bar. I was curious to know how closely the density of my bar was with the actual density of copper (about 8.96 g/cc). My bar measured 1 pound .5 oz (467.76 g). I calculated the volume two ways, water displacement and measurement; the volume is...

Homework Statement Suppose you take a pass-fail test repeatedly. Let Sk be the event that you are successful in your kth try, and Fk be the event that you fail the test in your kth try. On your first try, you have a 50% chance of passing the test. P(S1)=1−P(F1)=1/2. Assume that as you take the...

hi! i need to solve this integral: \rho_s=\int (m/\omega)e^{-\omega/T}d{\vec k} where \omega=\sqrt{m^2+{\vec k}} is the dispersion relation, T is the temperature of the system and m the mass of a particle Thank you!

If 50kg of salt is mixed with 100 kg of water to form a 1500kg/m^3 solution, can I find the concentration of salt by subtracting the density of water which is 1000kg/m^3, or do I have to equate it like this: 50/((50+100)/1500)=500kg/m^3 ? Is the volume of salt negligible so that the volume of...

Homework Statement An experiment to measure density, d, of a cylindrical object uses the equation d=m/(pir^2l) where m=mass=0.029 +-.005kg r=radius=8.2 +-.1mm l-length=15.4+- .1 What is the absolute uncertainty of the calculated value of the density? Homework Equations above The Attempt...

Homework Statement a) and b) are no problem. I need help to solve c) and d) Homework Equations c) Delta dirac function Gauss' law d) Gauss' law ## \int_V {\rho \, d\tau} = Q_{enclosed} ## The Attempt at a Solution By taking laplace on the potential I get: ## \rho(\mathbf{r}) =...

Is there any way to find the density of states from the IV graph

Homework Statement a) A material is composed of two atoms, A with effecitve radius 2.00 angstroms and B with effective radius 3.10 angstroms. The lattice is a body-centred lattice. b)Enter the volume density of either the A or B atoms in atoms/cm3 Homework Equations .5*sqrt3=(r1+r2) surface...

Hi, I was recently thinking about a problem which I have no idea how to solve. A full water container with volume V is hanged on a rope with length L (mass of the rope is negligible). It then starts to revolute around the point where the rope is hooked (circular motion, circle with radius L)...

Homework Statement I need to find three potential reasons for my .5% error in a lab where I used the Archimedes Principle to measure the density of Iron. We only used a graduated cylinder full of water and an iron mass. I measured the water level from the meniscus. We used two different...

Homework Statement Homework Equations and attempt at solution I think I got the ground state, which can be expressed as |\Psi \rangle = \prod_{k}^{N}\hat{a}_{k}^{\dagger} |0 \rangle . Then for the density matrix I used: \langle...

Derive the probability current density for a particle in an electromagnetic field. (I previously posted this on StackExchange. Please pardon, but I have been spending a lot of time on this and if anyone knows exactly what the subtle trick involved is, I would really appreciate it.)...

I have data which gives me the magnitude density (mag arcsec-2) of M31 as a function of radius. How can I convert this data to the (enclosed) mass at a given radius (for Velocity Curve analysis)?

Homework Statement We know that after long run of simple mass-spring system, there should be a probability of finding the mass at certain points between -A and A.. Obviously in probability of finding the particle near A or -A is higher than finding the particle at 0, because the speed is the...

Hi... any idea on how to calculate force needed to pull up something stuck on the ground? ex: Boot stuck on mud person sinking on quicksand or car sinking in water

G’day physics forum This is a purely hypothetical question and my knowledge of physics is rather limited so I’ve no idea if answering it is even possible however here goes: Imagine a 30cm long timber stick approximately 3mm in diameter that has been placed vertically in an inverted pyramid or...

Hi! I am a freshman in college on my first week of an intro chemistry course. I think the professor may have made a mistake with the software that generates the problem sets, but I'm giving it a shot regardless. One of the questions is: An alloy with a 1:1 ratio of magnesium and strontium...

This is a bit of a random project I am looking into. Recently a product was released called the beer bug. It measures the density of beer by tracking the weight of a submerged buoy. They calculate change in density based on changed in weight and then calculate % alcohol (ABV) from that...

Homework Statement A rather large non conducting slab of area A and thickness d has a charge density given by ρ = αx2. The origin is through the center of the slab. That is, it bisects the slab into two equal volumes of d/2 thickness and with an area A, with -L/2 to the left of x=0 and L/2 to...

Homework Statement "Calcium crystallizes in a body-centered cubic structure. (a) How many Ca atoms are contained in each unit cell? (b) How many nearest neighbors does each Ca atom possess? (c) Estimate the length of the unit cell edge, a, from the atomic radius of calcium (1.97A). (d) Estimate...

Homework Statement Perform potential energy W of a non-uniform density sphere by density d=d(r) and o(r)=dW/dm. Homework Equations The answer is W=1/2.integral(from 0 to R)(4x3.14xd(r)xo(r)xr^2xdr). The Attempt at a Solution I have solved this by this way: o(r)=-GM(r)/r...

Homework Statement Given a spherical shell of radius R and the surface charge density ( being the angle from the top of the sphere and being a constant) find the electric potential and the electric field inside and outside the sphere. Check that both the potential is continuous inside and...

This is a diagram of a pitot-static tube. My question is however not related to its applications but rather, what causes the liquid to rise up the static tube? The static tube is at right angles to the fluid flow. I understand that this is a very basic question but I can't seem to get my head...

Homework Statement Show that the density of water at a depth z in the ocean is related to the surface density rho_s by \rho(z) \approx \rho_s [1 + (\rho_s g/B)z] where B is the bulk modulus of water. Homework Equations B = -V (dP/dV) B = rho (dP/d rho) 3. The Attempt at a Solution I've...

At a temperature of 0 C the density of ice and liquid water is 0.9187 g/cm3 and 0.9998g/cm3 respectively. Consider a situation where the density of ice is increased to more than 8.83% at 0 C, what would be the consequences of this to the life forms? The life forms would vanish because of the...

Homework Statement So I saw a unit "W/(g2 cm3)" And I'm pretty sure it's about power density...and I understand what W/cm3 is. It's watts per cubic centimeter...but what does the g mean? grams? If so, how does that fit in? :/[/B]

Hi. Bell's formulation of local realism is $$P(a,b)=\int\ d\lambda\cdot\rho(\lambda)p_A(a,\lambda)p_B(b,\lambda)\enspace.$$ Let's for simplicity assume there's only a finite number of states, so this becomes $$P(a,b)=\sum_{i} p_i\cdot\ p_A(a,i)p_B(b,i)\enspace.$$ I'm trying to translate this...

I am confuse with the fact that current carrying conductor has gradual surface charge density which provide force to electron to produce current.

Hey All, I was wondering if anyone knows of any good simulation software packages that can do quantitative radiometry. I'm thinking COMSOL may have a radiometry suite, but I'm not very familiar with the software or package offerings. Basically, I'm trying to optimize the placement of hundreds...

Homework Statement You've probably noticed that TV screens and computer monitors have an annoying tendency to accumulate dust. Wanting to understand this better, you decide to model the situation as follows: you assume a small mote of dust might have an excess charge of 1 nC and a mass of 5...

Suppose we have an elliptical loop of wire in the x-y plane with constant cross-section. And let's also assume that the cross-section is very small, so we have a thin wire. $$\vec{r}=\begin{bmatrix} x \\ y \end{bmatrix}=\begin{bmatrix} a\cos \theta \\ b \sin \theta \end{bmatrix}$$ A tangent...

Hi, I'm trying to write the current density for such circular loop in spherical coordinates. For a circular loop of radius a that lies in the XY plane at the origin, the current density it's simply: \mathbf{J}= \frac{I}{2\pi\sin\theta}\delta(\theta-\frac{\pi}{2})\frac{\delta(r-a)}{a}\hat{\phi}...

Dear friends, Does anyone know how we can solve the TOV equations for a non constant density? In all the references, I just saw the solution for a constant density. Thanks in advance for the help :)

I'm sorry for my bad English. Let X a completely Hausdorff space. Will the be space of all continuous real-valued functions on a space X with the topology of pointwise convergence dense in the Tychonoff product ℝX?

I am doing research and I need to find the dark matter density of Galaxies or dust clusters (It can be any type of thing) which the distance from Earth will be ≅4000 Mpc.Here the picture Think the radius of sphere.

Dear Friends! Probably more than a decade back understanding tells us : If the average matter density of the universe happens to be smaller than a critical value,then the galaxies will never come to a halt and turn back(Open Universe).Which will imply cold and lonely death. If on the...

I've never been able to figure this out. I can understand when you put oil in water that one floats on top of the other, but why does it still work if I put it into a balloon? Something that keeps it from directly interacting with the medium it's in?

Everything as follows: I'm looking to calculate the amount of NaCl (rho=2.19 g/cm^3) needed to add to water (rho=0.999 g/cm^3) to achieve a solution with density=1.071 g/cm^3. Ideally, I want to achieve an Atwood Number of 0.035 and a density of 1.071 g/cm^3 is what I need for the solution...

Okay, so this is the website: <Moderator's note: link deleted as it is not a valid reference> I found this page as I was looking for a way to compare the assumed gravitational constant of the moon and the acceleration of the hammer/feather from the Apollo 15 experiment video. I have only taken...