0
votes
0answers
5 views

A box up an inclined ramp with a coefficient of friction [on hold]

A 6.25 horsepower motor to pull the boxes a distance of 8.35 meters up a ramp inclined at an angle of 36.2º with respect to horizontal. The boxes have a coefficient of kinetic friction of 0.381 as ...
1
vote
0answers
11 views

Extra-Solar System Global Warming?

The sun probably easily dominates in its impact on the atmospheric temperature of Earth. However, for roughly half of each day, each side of Earth faces away from the sun. Combined, the time spent ...
1
vote
0answers
10 views

Is a double integral required to find the moment of Inertia of a non-uniform sphere?

A sphere of radius $0.17m$ has a density $\rho$ described by the equation $\rho = 3500 kg / m^3 - (9500 kg / m^4) r$, where $r$ is the distance from the center of the sphere. What is the moment of ...
1
vote
0answers
12 views

what make the bottom portion of a wheel in rolling motion move?

As I just learn about the rolling motion which is the combination of pure translation and pure rotation. The top portion of the rolling body has the speed of double speed at the center of the object ...
0
votes
0answers
3 views

What is the force of the wind resistance? [on hold]

A sled of mass 15.0 kg is pulled forward with a force of 35 N. Also a frictional force of 12.2 N acts on the sled. Finally a wind resistance acts on the sled. Over a period of 18.0 s the sled ...
1
vote
0answers
11 views

Gauge choice after SSB

After the spontaneous breakdown of local symmetry in presence of gauge fields (Higgs Mechanism), we can always choose a gauge where the Goldstone bosons are eaten up by the gauge field. Which ...
3
votes
1answer
18 views

Center of mass frame for massless particles

Given a scattering event where a photon and electron go in and a photon and electron come out, what is the center of mass frame? I'd say, since the photon has no mass, it's the rest frame of the ...
3
votes
0answers
19 views

Two carts connected by spring on frictionless track

I have the following homework problem: Consider two carts of equal mass m on a horizontal, frictionless track. The carts ar5e connected by a single spring of force constant k, but are otherwise ...
0
votes
1answer
17 views

Two Limits in Thermodynamics - Reducing Driving Force and Increasing Resistance

I just wanted to clarify what is probably a very obvious idea. Suppose I'm holding a a piston separating two containers at different pressures. If I release the piston, it will naturally move, ...
1
vote
1answer
16 views

Say, a liquid is made to flow in a tube. Why does the layers of the liquid in contact with walls of the pipe have zero velocity?

Say, a liquid like water is made to flow in a pipe. Why does the layer of water near the walls of the pipe have zero velocity? Does that mean that the layer of water near the pipe is stationary and ...
-2
votes
1answer
20 views

What causes the recessed blade of some folding knives to emerge in a kinetic opening?

KINETIC OPENING OF FOLDING KNIFE (FK) Several legal jurisdictions around the World, including Australia, have assented legislation/regulation which attribute the emergence of the recessed blade in the ...
0
votes
1answer
4 views

Determining flexural modulus by performing 3 point bending test using hollow cylindrical tube

I would like to decide the flexural modulus of the material of plastic tube by performing 3 point bending test according to the ASTM D 790 procedure. In ASTM D 790, the form of the specimen is ...
1
vote
3answers
26 views

Mathematical Reasoning for Fluid Pressure as a Scalar

This question from a while ago and answers/comments to this question from earlier today both make heavy mention of the fact that fluid pressure is a scalar. Although this information was surprising ...
-2
votes
2answers
27 views

Flea jumping question

During a takeoff a flea develop a acceleration of $3m/s^2$ it reaches a max height of 36mm. How long does this acceleration last? Finding initial velocity is fairly easy but the finding the time ...
0
votes
0answers
12 views

Projectile Aiming [on hold]

I'm having a but of trouble with a game I'm programming. What I have is an enemy who periodically shoots a laser at the player if they're close enough. I've been trying to come up with a way to make ...
-1
votes
0answers
22 views

At what velocity does space no longer equal a vacuum? [on hold]

In Dr. Alistair Reynolds's book (Revelation Space), he mentions that space only equals a vacuum at low speeds. At which velocities would space no longer count as an almost vacuum?
0
votes
0answers
17 views

Normalize human motion

I'm working on human motion recognition. I have question about normalization. Based on the literature, there are many methods used for normalization. I don't understand how there do normalization, ...
-2
votes
0answers
14 views

Leptons slide between quarks? [on hold]

I wonder if one of particles (maybe quarks?) are constructors of highways in 3d field for others floating around re/distributing energy by some (leptons?), restricted to laws set by (bosons?). If ...
0
votes
0answers
30 views

No length contraction!

Suppose a person standing on a platform were to observe and measure the length of a train passing by. Instead of the usual approach involving a clock and knowing the speed of the train, the person ...
0
votes
0answers
10 views

Role of the crystallographic point group on properties of tensorial elasticity

If a space point group for a crystal is known, does this automatically define the elastic tensor symmetry of the material? What further implications can be found? The crystallographic subgroups: ...
3
votes
1answer
33 views

Fruit flies in a bell jar

You place a bell jar on a scale and the scale registers x grams. You then trap y grams of flying, non-landing fruit-flies in the bell jar. What does the scale register? x grams? x+y grams? Something ...
0
votes
1answer
11 views

Latent heat of solidification

What is the heat release mechanism involved in solidification from liquid phase? Is the energy transferred to nucleation centres?
1
vote
1answer
18 views

Evaporation of water at room temperature

Could anybody refer me to some literature (textbooks or research, although preferably textbooks!) dedicated to explaining quantitatively the phenomenon of evaporation of fluids? I understand that it's ...
0
votes
1answer
35 views

Hooks Law and acceleration

A 435 gram sharpened piece of iron rebar into a spring loaded device. It takes a force of 355 Newtons to compress the spring by 27.5 cm. With what speed does the rebar shoot out of the device? ...
-8
votes
0answers
20 views

What is the speed of times arrow [on hold]

If the maximum speed of time in a vacuum is C you would have included time in relativity theory and have a definition of space time, Or the mass-time equivalence. A thought experiment.
0
votes
0answers
12 views

How non-invasive blood glucose concentration measurement work? [migrated]

Diabetes patients need to conduct the “fingerstick” a few times a day. One of the mechanisms of "fingerstick" is to take small amount of blood sample and put it onto a test strip. The enzyme on the ...
0
votes
1answer
40 views

Do we exist in multiple dimensions?

I have heard that there are 12 spacial dimensions. Does this mean that this many are possible,or that 12 dimensions actually exist? If the ladder, then do the same things that exist in 3 dimensions ...
1
vote
3answers
35 views

Determine which circuits are parallel and which are in series

I need to find the Equivalent Resistance across A and B. The problem is, I don't know which one's are in series and which ones are in parallel. How do I identify which ones are parallel or series?
1
vote
3answers
21 views

Sound diffraction through a single slit

When sound waves diffract through a single slit, do they produce an interference pattern which is mathematically identical to that of light waves in the corresponding experiment?
0
votes
1answer
33 views

Two Particle System with Identical Particles

I'm studying for an exam in quantum mechanics and tried to calculate the ground state and the first two excited states of two identical bosons (spin 0) in an infinite one dimensional potential well. ...
1
vote
1answer
28 views

Pressure and variation in pressure due to depth

In my class, we were shown the following problem: Using the equation $P_1$ = $P_0$ + $\displaystyle\rho$gh, where $P_1$ is the pressure at Superman's mouth and $P_0$ is the pressure at the surface ...
0
votes
0answers
6 views

Physical meaning of Orbital Polarization

In this paper, the Orbital Polarization (OP) is defined as: $$OP=\frac{n_{x^2-y^2}-n_{z^2}}{n_{x^2-y^2}+n_{z^2}}$$ where $n_i$ is (I suppose) the occupancy of that given orbital. I would like to ...
-1
votes
0answers
15 views

Uniform motion - need help with this problem [on hold]

Body A is moving towards body B (which is moving to A) with speeds v1 (for A) and v2 (for B) on the road s.Body B starts moving after time Δt compared to the body A (so t2 = t1 + Δt).I want to know ...
-4
votes
0answers
17 views

Law of conservation of linear momentum is a consequence of Newton's forst law substantiate [on hold]

Law of conservation of linear momentum is a consequence of Newton's first law substantiate.
0
votes
2answers
51 views

If Earth starts moving when attracted by an object, where does the energy come from?

Suppose a body(very big but not bigger than Earth) moves against gravitational force of Earth. The force will do negative work on the body decreasing its kinetic energy. The decreasing energy is ...
9
votes
2answers
81 views

Topology of phase space

Context: From Liouville's integrability theorem we know that: If a system with $n$ degrees of freedom exhibits at least $n$ globally defined integrals of motion (i.e. first integrals), where all ...
1
vote
1answer
43 views

What wilI I observe when travelling at almost the speed of light? [duplicate]

If I and a group of friends are travelling at or just below the speed of light - can I see myself, can I see them, or they me? Would we see anything at all?
3
votes
0answers
49 views

Difference in “momentum” names in Lagrangian mechanics

In the context of Lagrangian formulation of classical mechanics, the following names keep occurring in most textbooks, which confuse me a lot, are they different in any way? Momentum Generalized ...
1
vote
3answers
79 views

Variational Theorem proof

I have been trying to prove variational theorem in quantum mechanics for a couple of days but I can't understand the logic behind certain steps. Here is what I have so far: \begin{equation} ...
1
vote
0answers
44 views

Metric with 5D signature: +---+

From a paper that a friend sent to me (on inflation theory which I am still in learner mode) a 5D signature +---+ was specified with the 5th dimension being a velocity dimension. I didn't know that ...
0
votes
0answers
14 views

(Optical) Coherent states being all orders coherent

I recently read that coherent states $|{\alpha}\rangle = e^{-|\alpha|^2/2} \sum_{n=0}^\infty{\frac{\alpha^n}{\sqrt{n!}}|{n}\rangle }$ are all orders coherent, according to the definitions given on ...
1
vote
0answers
13 views

How to calculate the $g$ degeneracy factor for alkali metals and their singly ionized species?

The Saha ionization equation is $$\frac{n(X_{i+1})}{n(X_{i})} = \frac{(2\pi m k T)^{1.5}}{n_e h^3}\frac{2g_{i+1}}{g_{i}}e^{-\chi/kT}$$ where $\chi$ is the energy difference between the two ...
1
vote
2answers
33 views

Index notation with Navier-Stokes equations

This is an index-notation question rather then the NS one: For incompressible flow and Newtonian fluid, the continuity equation is denoted with: $$\frac{\partial u_i}{\partial x_i} = 0, $$ which ...
0
votes
0answers
13 views

Uncharged Gluon Representation

I'm currently learning for an exam and in an old exam the question was posed: If Gluons were uncharged, under which representation would they transform? The ...
1
vote
2answers
36 views

For a massless pulley moving upwards with acceleration, is the upward force equal to the downward force?

Imagine a massless and frictionless pulley with two weights hanging either side of the pulley by a massless string. Like this except not attached to a ceiling Rather than being fixed to a ceiling, ...
0
votes
2answers
33 views

Direction of pressure in fluids

ok so my friend told me that in a container, the pressure exerted by the walls on the liquid in the container act in the upward direction.Is he correct ? so what I am imagining is a cylindrical ...
2
votes
2answers
38 views

Why aren't classical phase space distribution functions always delta functions?

The phase space distribution function (or phase space density) is supposed to be the probability density of finding a particle around a given phase space point. But, classically, through Hamilton's ...
1
vote
0answers
20 views

Who makes the astronaut helmet visors for NASA? [on hold]

I am searching patenting sites for information regarding visors. Results are varied by specific uses. To feel comfortable with my search, I think the specific use is comparable to that of the visors ...
0
votes
1answer
29 views

Recent important observations on dark matter [on hold]

I would love some suggestions about my undergraduate research, thought it may be improper to ask here. I apology if I break the group rules. My undergraduate research topic is dark matter. My plan ...
0
votes
0answers
16 views

Semiconductor band diagram with a doping gradient

What does the Energy band diagram in a semiconductor look like if we introduced a doping gradient? What would it look like if after we added the doping gradient we introduced an electric field? I ...

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