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2

In the case of inorganic matter, such as metal sheets, folding/creasing produces a substantial bulk stress in the material which can modify the molecular structure in a large number of complex (and not fully understood) ways. For example, it can break bonds, cause amorphisation, and propagate dislocations. These same mechanisms are at play when you cut a ...


2

What happens during folding is that the material undergoes plastic deformation. When a sheet of material is bent slightly that deformation is usually elastic, meaning it will return to its original shape when the deforming stress is withdrawn. But when the deformation is larger we enter the plastic zone: the material will no longer fully recover its ...


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A 40W incandescent light bulb has a luminous efficiency of 1.9%. That means only 1.9%, or 0.76W, of the energy consumed by the bulb ends up as visible light. LED bulbs have an efficiency of around 10% - the efficiency depends on the design and can be as high as 15% or as low as 8%. So a 6W LED bulb will produce between 0.9 and 0.48W of visible light. The ...


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You're mixing power needs with luminous effects. According to the advert you posted, that LED bulb consumes 6W (power) to get a luminous flux of 500 lumens (lumen is a photometric unit, like candela or lux): https://en.wikipedia.org/wiki/Luminous_flux On the other hand, an incandescent bulb would need to consume 40W (power) to get the same luminous flux. ...


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The advertising suggests that the new 6W bulb generates as much light as a 40W incandescent light used to. Most of the energy in an incandescent light bulb is converted into infrared radiation that we can't see or it's at the red end of the spectrum where the human eye is not very sensitive. This is a typical incandescent spectrum and you can see how ...


4

Edited because I had misread the question If the goal is to keep the tea hot, you add the milk first. This will bring the temperature of the tea down by some amount $\Delta T$, and the cooler tea will now lose heat more slowly while you dissolve the sugar. I am assuming that since you cannot see the sugar in the milky tea, you will do what I do - you add ...


2

It needs energy to solve sugar in water because the enthalpy of solvent (water) and solute (sugar) is lower than the enthalpy of the final solution, solving is an endothermic reaction in this case[1]. Milk has already some sugar in it, the (in)famous lactose, so the enthalpy of tea+milk might be higher than the enthalpy of tea alone and the order "milk ...


4

If the processes are instantaneous, and you drink the tea at once after that, then it doesnt matter. A more interesting question would be, when to put the milk in the tea. Now it does matter if you wait first and then add the milk and drink - or if you add it at once and then wait and drink. Do you see, why? Also, in your formulation "you were asked to ...


2

The order doesn't matter. The reason is conservation of energy. The tea, milk, and sugar before the mixing have some initial energy, and the final tea will have some energy that depends only on its state (the tea doesn't have any kind of memory of how it got to that state). The energy difference between these two states is the additional energy associated ...


0

My proposed explanation is in the thickness. We wish the headphone wires thin and shoelaces thick. The former favors fixing sharp bends by entangling them randomly, the latter favors straightening them. If we tolerated 5 mm thick nylon yarn around our headphones, they would certainly tangle much less.


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Yes, your myopia is relevant in the sense that you notice immediately a huge improvement in your long distance vision when wearing goggles underwater. Short-sighted people have difficulty in focusing distant objects (or nearly parallel light rays); the eye is "too long" for the lens and the focus falls in front of the retina. Corrective lenses for myopia ...


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Is blurred effect due to turbulence? No, it is not. The turbulence has a little effect here. Even if there is no turbulence, one see everything blurred underwater. The reason is explained below. An eye is a natural lens. A clear shot of something you see depends on how well the image is focused on your eye. The most of the refraction in the eye occurs ...


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The reason is the same as with non-newtonian fluids. As you can see there, the work done is not independent to the rate. If you do it with lower velocity, you can get through with less work. There is a lot of Video's from these "non-newtoniand Fluids" in youtube. The reason why this is so, lies on the understaning of Turbulence; Turbulent water is less ...


2

Exact mechanism varies with material, simple materials (non-organic) are easier to analyze. Simplest answer is if you bring them together they will join, provided size is small. For example in Cold Welding less than 10 nm wire is rejoined just by contact. The exact mechanics depends on what kind of Intermolecular force is in play. According to Grove Karl ...


1

LCD displays use three layers: a polarizer, which polarizes the light produced by the backlight system a liquid crystal, which has the ability to twist or not the direction of polarization of light, controlled by an electric field another polarizer, called analyzer, stops or not the light out of the liquid crystal, depending on it having rotated or not the ...


1

Adhesion is not stronger at faster peeling rate. If we formally associate adhesion as "the amount of energy needed to separate two parts", then we can describe it physically by the potential joining those two parts together. In classical mechanics, where potentials are independent of time, like in gravitation or electrostatics, you can still explain why it ...


3

The crucial word here is rate. When pulling one gives a dp/dt, momentum to the pulled tape, which is the force that is applied. This can be given as delta(p)/delta(t). For the same transfer of momentum delta(p) to the unstuck tape, a smaller delta(t) (faster) will result in a greater force. This can be exacerbated because one gives a bigger momentum to the ...


1

Since the hard drive platters are relatively heavy, and spin at a very high speed (7200 rpm for most hard drives, and even 10000 rpm or more for high-performance drives), the hard drive becomes one big gyroscope. If you've ever seen a gyroscope toy, you've observed gyroscopic precession firsthand. When you turn your hard drive along any axis other than the ...


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Adhesion (wiki) can be due to several phenomena. In some, the adhesive is a very viscous liquid which will slowly deform (or "flow") with a small applied force.


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Yes there is. You can estimate by experimenting and playing with a magnet calculator until the pull force numbers match up.


2

1) What can be say about the work done by the man to the weight? Unlike gravity, the force exerted by the man is in general not constant, does not depend only on position of the body (you may apply different force on the weight at the same height $h$ on the way up vs. on the way down), and is not conservative (does not arise from a potential). When the ...


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1&2) Let's suppose there are only two forces in play: the one exerted by the man, and weight. The sum of works done on the body equals the variation of kinetic energy (this is a theorem of mechanics; I fail to find its English name). Since the body has no velocity at the start and at the end, the sum of works is zero. The net work done by the man on ...


1

The correct statement is - the total work done on the weight is zero i.e. the total energy of the weight before and after the experiment is same. However, when the man is lifting the weight he is obviously working against gravity. More importantly, when he is lowering the weight, he is still working against gravity, as gravity would rather lower the weight ...


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There are three pigments in the human eye cone cells and combinations of their light sensitivities are the basis of our color vision. These pigments are red, green, and blue. The violet end of the spectrum excites blue pigment only. Less-extreme 'blue' perception includes some slight green pigment response. The color that results from red and blue ...


1

Although the Sun is much wider than the Earth it produces sharp shadows on a clear day since its angular width from Earth is very small. The slightest mist reduces the sharpness of the shadow. At night a bare light-bulb produces a much sharper shadow than the same bulb inside a diffuser, such as a Chinese lantern.



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