1. ### I Does the 1 Second after the Big Bang = 1 second now?

When I read that conditions were such and such 1 to .05 seconds after the big bang, is that duration somehow longer than 1/2 second is now (maybe because of the difference in density or like the twin paradox?)?
2. ### Water level involving Density, mass, volume, radius

Homework Statement A small solid sphere of mass M0, of radius R0, and of uniform density ρ0 is placed in a large bowl containing water. It floats and the level of the water in the dish is L. Given the information below, determine the possible effects on the water level L, (R-Rises, F-Falls...
3. ### A solid cylinder of uniform density of 0.85 g/cm3 floats in

Homework Statement A solid cylinder of uniform density of 0.85 g/cm3 floats in a glass of water tinted light blue by food coloring. https://s1.lite.msu.edu/res/msu/kashy/physicsLib02/32_Fluids1_Pascal_Arch/graphics/archimedes.gif Its circular surfaces are horizontal. What effect will the...
4. ### A small solid sphere of mass M0, of radius R0, and of unifor

Homework Statement A small solid sphere of mass M0, of radius R0, and of uniform density ρ0 is placed in a large bowl containing water. It floats and the level of the water in the dish is L. Given the information below, determine the possible effects on the water level L, (R-Rises, F-Falls...
5. ### Find Density Given Period of Orbit

Homework Statement A satellite is in a circular orbit very close to the surface of a spherical planet. The period of the orbit is 2.53 hours. What is the density of the planet? Assume that the planet has a uniform density. Homework Equations T^2=(4pi^2r^3)/GM V=4/3piR^3 Density= Mass/ Volume...
6. ### B Singularity vs. Black Hole

What has a higher density? Black Holes or Singularities? I looked online and all I saw was that they both have infinite densities.
7. ### Question about polarization density

Homework Statement Given a sphere with radius R, centered at (0,0,0), it's dipole density given as ##P\left(\vec{r}\right)=\alpha\left(R-r\right)\hat{z}## where r is the distance from the center of the ball. I'm required to find: Bound charge density inside the sphere, bound charge density on...
8. ### I Question: pressure inside an object submerged in water

I'm doing a question relating to the pressure inside on object submerged in water. Here is the question: A tube, height 1.2m, is submerged vertically in the ocean where the waters density is 10^3 kg/m^3. A diver initially holds the tube vertically directly on top of the water. He then dives to...
9. ### Specific Gravity of a Brine

Hello all, I am currently trying to convert brine salinity values in ppm to the corresponding brine density. My understanding is that I can do that using ppm * SG = mg/L . However I do not know how to get the Specific Gravity (SG) of my brine. The data I try to convert has a minimum value of...
10. ### Density floating problem, wood and lead

1. Homework Statement A block of wood has a mass of 3.47 kg and a density of 628 kg/m3. It is to be loaded with lead (1.13 × 104 kg/m3) so that it will float in water with 0.848 of its volume submerged. What mass of lead is needed if the lead is attached to (a) the top of the wood and (b) the...
11. ### I Rotational Inertia Gas vs Liquid

I am conducting an experiment that rotates a sealed donut cylinder to investigate amongst other things the inertia of the contained fluid. Process I rotate the cylinder to a set speed (assuming that the viscosity of the internal fluid will end up rotating the fluid to solid body rotation)...
12. ### Compute the magnitude of the current density

Homework Statement Copper and aluminum are being considered for a high‐voltage transmission line that must carry a current of 51.4 A. The resistance per unit length is to be 0.176 Ω/km. Compute the magnitude of the current density for an aluminum cable. Homework Equations R\quad =\quad \frac {...
13. ### Find the magnitude of the current density

Homework Statement A beam contains 3.95×108 doubly charged positive ions per cubic centimeter, all of which are moving north with a speed of 1.64×105 m/s. What is the magnitude of the current density? Homework Equations J = nev n = electron density e = electron charge v = drift velocity The...
14. ### What is the total mass of the atmosphere?

Homework Statement Problem from the book "Engines, Energy and Entropy", Page 55, question 7 has me stumped. It doesn't feel like their is sufficient information to work out the mass of the air. They've given us density (as seen in the picture, if the upload works) , which is mass over volume...
15. ### How to find Lagrangian density from a vertex factor

Homework Statement This isn't a homework problem, per se, in that it's not part of a specific class. That being said, the question I would like help with is finding a Lagrangian density from the vertex factor, $$-ig_a\gamma^{\mu}\gamma^5.$$ This vertex would be identical to the QED vertex...
16. ### Volume of a Floating Object

Homework Statement If a 5kg object floats in water (density=1000 kg/m3) with 20% of it's volume above the surface of the water, what is the volume of the object? Homework Equations Archimedes' Principle = the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or...
17. ### Mass of half ball

Homework Statement If the density of the half-ball x ^2 + y ^2 + z ^2 ≤ 4 ; z ≥ 0 is given by δ(x, y, z) = ( x^ 2 + y^ 2 + z ^2)^(1/2) find its mass. Homework Equations ∫∫F⋅ds ∫∫FoΦ(u,v)||Tu,Tv||dudv ∫∫FoΦ(u,v)⋅(Tu,Tv)dudv The Attempt at a Solution For the last problem I was asked to find...
18. ### Measuring the Density of Air

Homework Statement Measure the density if air at normal atmospheric pressure. You can use the following equipment: One scale with an accuracy of 0.01g Two empty glas bottles (≈0,33 liter each) One big bowl with water One cork with a valve and a vacuumpump Homework Equations Not knowing how...
19. ### Physics Archimedes Principle Distance an object sinks

Homework Statement A block of wood measures 2.2m by 2.5m with depth 3.6m with weight 102KN. When placed in water, how far will it sink? g = 9.81 ms-2 density of water = 1000kg m-3 Homework Equations The Attempt at a Solution Volume = 2.2(2.5)(3.6) = 19.8m3 Mass = 102000 / 9.81 = 10398 kg...
20. ### Bridge Project

Homework Statement Hi! I wasn't sure how to ask this, but my team and I are making a manila file folder bridge and we are stuck a specific part. We are looking to get the mass of the members and we decided to get it through multiplying the volume of the member by the density of manila file...
21. ### Change in density due to thermal expansion

Homework Statement I want to find the mathematical proof to show that the density of an object changes with thermal expansion. My professor showed this in class and it was horribly wrong because he let a few things out. The book I'm reading showed it in 4 steps and left out a lot of the crucial...
22. ### Why did my glass bottle explode?

Five days ago, I filled a glass 2L bottle about halfway with litchis, then filled the bottle with water till the end and sealed it with its cap. I was curious to see how it decomposes in there. This morning, about 1/7th of the water was lying in a puddle around the bottle. I could see gas...
23. ### Stator inlet angle in turbomachine?

Hello, I am wondering about the following action in a stator: If the inlet angle in a stator is B, and the outlet angle is -B, what exactly is happening? Axial vlocity should be constant, and so should the relative velocities except being mirrored and i am asuming infinitely thin blades.. Can...
24. ### Electric arc in 0 gravity? Curved or straight?

I observe that electric arc forms a curve. I think that this is because electric arc is extremely hot and hot air goes up because it has less density. So if electric arc occur at 0 gravity would it be straight? from wikipedia https://en.wikipedia.org/wiki/Electric_arc Thank you.
25. ### Buoyancy Force

Homework Statement If you have a body that weighs 100 N dipped in oil that has density equal to 0.8 g / cm³. This same body when immersed in water begins to weigh 60 N. How do I find the density / specific body mass? Homework Equations Solution= 1,3 g/cm³ The Attempt at a Solution Already...
26. ### Insulator density and thermal conductivity

How does insulator's density affect its thermal conductivity? For example, considering such insulators as rock wool, It seems that the thermal conductivity should increase with an increase in density (due to elimination of 'air pockets'). However, experimental results, in many cases, look more...
27. ### Density: Cube of Aluminum to Copper Sphere

Homework Statement What is the diameter of a copper sphere that has the same mass as a 9.00 cm× 9.00 cm× 9.00 cm cube of aluminum? Density of Aluminum = P(al) = 2.70g/cm3 Density of Copper = P(cu) = 8.96 g/cm3 Volume of Aluminum Cube = Vcube = 729 cm3 Homework Equations Volume of a Sphere =...
28. ### How is light affected by the gravity of a black hole?

Hello! I am new to this forum, but I'll give it a shot. It is my understanding that photons have no mass- but that light is still pulled by the gravity of a black hole. How can something without a mass, and therefore, gravity, be pulled by the gravity of another object? Any insight would be...
29. ### Deuterium and Tritium Density

Hey, I've been searching around online, and I can't find anything on the individual densities of D2 an T3, only the mean density of all hydrogen isotopes. Thanks, NWFusor
30. ### How to densify silicone oil?

Hi everyone, I am looking for a way to densify silicone oil. Foolishly, I tried to dissolve Calcium Chloride but as well all know, salt will not dissolve in oil. If anyone has any knowledge as to how I can increase the density of silicone oil I would greatly appreciate your input.