The study of how the properties of matter arise from its structure at all scales and of how processing can be used to modify those properties (often in pursuit of a specific application).

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42 views

Optical Retroreflectors: How Are the Faces So Accurately Righted?

This question is about Optical Retroreflectors (corner cubes) and how the extreme precision in their manufacturing is achieved. I suspect there is interesting basic physics involved, which is why the ...
0
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1answer
44 views

Determining a constant from two equations [on hold]

I am an engineering undergraduate taking a materials science module and i am having some trouble with the mathematical execution of the following question: Determine the constant in the equation for ...
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2answers
20 views

P-n junction diode under forward bias configuration

Why there is exponential growth in current with respect to voltage in p-n junction diode under forward bias configuration?
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2answers
33 views

Why chromium is more brittle than iron at room temperature?

Why is chromium more brittle than iron? I understand that both of them are BCC at room temperature. Is it to do with the grain size, and why is it different between the two metals?
4
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1answer
58 views

Is diamagnetism a static or dynamic effect?

When we put a diamagnetic material in the presence of an external magnetic field $\vec B_0$, the magnetic field inside the material decreases to $$\vec B=(1+\chi_m)\vec B_0,$$ where the magnetic ...
4
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1answer
46 views

Breaking strength of wet paper/cloth

In the Hollywood movie, Shanghai Knights (pardon me for the non scientific citation), Jackie Chan states that 'wet cloth' does not break easily. How true a fact is this ? We know from common ...
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0answers
18 views

Poisson's ratio and change in volume

The Poisson's ratio $\nu$ is always less than $0.5$. A traction force ($\Delta L >0$) can cause an increase in volume, while a compression force ($\Delta L <0$) can only decrease the volume. ...
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1answer
69 views

Why a bullet leaves a hole on glass where stone makes scratch?

When we throw a stone it breaks the glass with scratches. But when a bullet hits the glass it leaves a small hole(not always) . I want to know the specific reason behind making hole and scratch.
4
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1answer
38 views

Why does melted agarose in solution appear fully transparent, but become opaque when polymerized?

Agarose gels (hydrogels) are commonly used in molecular biology for electrophoresis of DNA. When a solution of hot agarose is poured, the material is clear: When a gel forms, the material ...
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0answers
10 views

How does one go about designing a substrate heater for PVD? I need to design one that can go till 1000 C in Oxygen.

Can I just use a Kanthal wire and make a pattern on a ceramic base? Wouldn't such an exposed element get shorted when I use substrates like Silicon? But wouldn't a layer of ceramic on top of the ...
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0answers
17 views

Springs and Cantilevers - how linear and repeatable are they under deformation?

I know you guys only deal with the ideal, but in practice how linear and repeatable is the response of a spring or cantilever when deformed under a test mass?
2
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1answer
32 views

Difference between dielectric and insulators

AS per my knowledge - dielectric are insulators which can be polarized in presence of external electric field. Does that mean all Insulators are not dielectrics ? If yes then kindly share example of ...
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0answers
41 views

Lab experiment: hysteresis disappears, reappears and then disappears again. How?

In my college laboratory we were assigned an experiment to measure the hysteresis curves of a certain ferromagnetic material at different temperatures. Sounds simple, right? Well, the block of Monel ...
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3answers
1k views

Why don't metals damp vibrations?

Fluid damps vibrations due to viscous dissipation. Does anyone has any insight on a molecular, microscopic level about the reasons that vibration damping of metals is negligible?
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2answers
59 views

Why an impact exerts so much force? [closed]

If an object of velocity $v$ and mass $m$ moves towards a resting object of mass $M$, then if the object which is hit might break. Why? What is the reason that a collision has more power than a ...
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0answers
20 views

How does the shattering of an amorphous solid change in lower gravity?

This is a question that's been bothering me for a while. If I were to stand on the moon, holding a pane of glass, what would happen if I smashed it? Glass is an amorphous solid, which is why it is ...
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0answers
20 views

Mechanical properties crown cap [closed]

What are the important mechanical properties to look at when designing a crown cork and why? Thank you in advance
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4answers
1k views

Are insulators and conductors arbitrary categories?

I have seen charts showing the transition from insulator to semi-conductor is at $10^{-8}~\frac{\text{S}}{\text{cm}}$ and between semi-conductor and conductor is $10^{3}~\frac{\text{S}}{\text{cm}}$. ...
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2answers
29 views

Reason behind heating the substrate in Pulsed Laser Deposition

Why do we need to supply a constant heat to the substrate while depositing thin films in Pulsed Laser Deposition technique?
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2answers
34 views

Can you dent a metal wall with a feather?

I know that theoretically you can only scratch a material with a harder material, but what about denting? While scratching a solid would seem to involve breaking bonds, denting a solid would ...
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0answers
31 views

How strong could a carbon nanotube be?

I was thinking about the limits of flywheel energy storage and wondered about carbon nanotubes. The amount of energy that can be stored per unit mass in a flywheel depends not on tensile strength but ...
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0answers
5 views

Height of a point in a plane given a measure of luminance

Context Assume a left-hand rule coordinate system and X points right, Y points up, Z points out. I have a camera facing perpendicular to the X-Z plane in the negative Y direction. I have 4 ...
6
votes
1answer
98 views

Why do headphones tangle themselves whereas shoe laces untie themselves?

Why do headphones tangle themselves whereas shoe laces untangle or untie themselves? Why aren't we using the phenomenon to create headphones that tangle less and shoe laces that untie less?
1
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1answer
30 views

Tensile strength of a chain of electromagnets

I was having a discussion about the tensile strengths of various materials. Could something like a chain of electromagnets be made to have a tensile strength proportional to the power applied to it? ...
0
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0answers
31 views

Why should we use good conductors as electrodes of a capacitor?

I was asked if and why why should the electrodes of a capacitor should be good electrical conductors. It seemed obvious to me that if I want to form a Helmholtz double layer (because that's what ...
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2answers
46 views

Is there any material that can survive a nuke? [closed]

Is there a material known to man that I can tape to a Tsar-Bomba-yield nuclear warhead and find kilometers away after detonation? This question is quite similar but a nuclear explosion is quite ...
0
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2answers
58 views

What causes tensile stress to decrease after a material/wire reaches its ultimate tensile stress?

I was reading the AQA A Level Physics revision guide by Jim Bretihaupt, and in the Materials chapter in the section to do with plastic deformation, it says: Beyond the ultimate tensile stress, the ...
0
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1answer
25 views

Would a bullet damage a piece of metal the same as a pointy stick?

If you used a materials that would offer zero bending or dulling (the bullet/ pointy stick), would a 10 g bullet traveling at 1000 m/s with a surface area of 1 mm squared damage a piece of metal the ...
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0answers
9 views

Does the rate of pressure change matter when measuring the strength of a closed container?

If I had a container that could hold 100 psi, and I increased the pressure to 100 psi instantly would I cause any excess stress on the container, or would it not make a difference from doing it over ...
0
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1answer
21 views

Material that reflects only a certain polarization?

Do materials exist that (significantly) reflect one polarisation of light and transmit all others?
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0answers
17 views

Copper vs Tungsten (Diffusion)

I've been studying on how to compare the activation energy for (void-) diffusivity of Copper versus Tungsten. I ended up finding $E_a[cu] = 1.1[eV]$ and $E_a[W] = 5.2[eV]$ in literature where the ...
0
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1answer
41 views

How to reduce size of bracelets using physics?

My mom has a set of bangles (bracelets) made of gold like the ones shown in the picture. Problem is the size (diameter) of these bangles is a bit more than required. If she goes to a goldsmith he cuts ...
0
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1answer
55 views

Is a laminated padlock really stronger than a solid one, and if so, why?

I used to think that the padlock design of using many layers of metal stacked to form the main body was a cost-cutting consideration. This was my assumption before I came across the idea that it was ...
1
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1answer
52 views

When you push a stick will the end of it respond later than the beginning? Is so what is the fastest material and what forces are involved?

Normally when two people hold a long stick the receiving person would feel at the same time the stick moving when the first person gives the stick a push. But is that in reality exactly the case? ...
0
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1answer
35 views

Calculating the Coefficient of Restitution Based on two Objects

The coefficient of restitution is calculated based on the velocities of objects before and after a collision: $$C_R = -\frac{v_{2f} - v_{1f}}{v_{2i} - v_{1i}}$$ The coefficient of restitution tells ...
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0answers
23 views

Armco iron B-H curves [closed]

I've been looking for B-H curves for Armco iron. I'd love to find one with good resolution. Does anyone know where you could acquire one? I've been looking in various Armco ingot supplieres but no ...
0
votes
1answer
38 views

Why can't we build a styrofoam 747?

What properties of materials explain why building the same structure at different scales requires materials of different densities and strengths? Consider an airliner, and flying models thereof at ...
3
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2answers
373 views

Does metal under low tension ever actually bend?

Let's assume something like a pair of tweezers, since that's strangely what led to this mental exercise. Does the metal ever actually permanently transform its shape? Stainless steel is fairly ...
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5answers
189 views

Is this a fundamentally relativistic phenomenon?

This question was inspired by some silliness in other threads but is independent of that silliness. Say that a train car sitting on a track is accelerated uniformly along its length if each point on ...
7
votes
1answer
133 views

Invariant polynomials of the Landau theory of phase transitions (crystal symmetry?)

I'm convinced I'm missing something so obvious but here goes Typically, one can define something like a "general" expansion of an order parameter, ${\boldsymbol \Gamma}$, up to 6th order as follows ...
0
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1answer
53 views

Why a balloon explodes by itself? [duplicate]

I was wondering why a balloon explodes after some time by itself with no specific reason. yesterday I was doing my chores and to my amazement the balloon far in the corner of house pop with no obvious ...
76
votes
9answers
14k views

Why does matter exist in 3 states (liquids, solid, gas)?

Why does matter on the earth exist in three states? Why cannot all matter exist in only one state (i.e. solid/liquid/gas)?
0
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1answer
57 views

Tabletop Synchrotron

When I was undergraduate student I asked to my proffesor why nobody has made a synchrotron machine with a superconducting circular wire and magnetic field to accelerate electrons properly and to ...
2
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0answers
33 views

Why is the moon white? [duplicate]

Why is the Moon white? What is it's geological composition and how does that relate to it's apparent "color"?
0
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0answers
13 views

Why are some plastics flexible at low temperatures and some not?

Is there any general predictors for the flexibility of plastics as the temperature drops?
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0answers
31 views

Thermistor is more sensitive than metals [closed]

Can anybody tell me, why a thermistor is much more sensitive at temperature variation than a metal?
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0answers
22 views

Pressure vessel analysis of transversely isotropic multilayer material

Suppose I have a transversely isotropic, hyperelastic material with known strain energy that is a fibrous composite. I am interested in an explicit formula for the displacements (so I can get the ...
1
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1answer
27 views

Are all FCC structures ductile?

Doing research on crystal structures and the effects of Ductile to Brittle transition at different temperatures. Results of this test proved aluminium to be a brittle structure, which I know to be ...
-1
votes
2answers
31 views

Can we enhance a thermal gradient by combining a dark surface and a shiny surface with an external glass layer?

I refer to the article at this site: http://solarcooking.wikia.com/wiki/Solar_Kettle-Thermos_Flask As we know, dark surfaces absorb radiation (eg. solar water heater), while shiny surfaces reflect ...
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0answers
11 views

Do Body Centre Cubic Structures become more ductile when subject to higher temperatures or does it remain brittle?

Doing some research on crystal structures and if they experience brittle to ductile transition when subject to different temperatures. I am aware that BCC structures become very brittle at low ...