23

For steel wool the combustion reaction is roughly: $$\require{mhchem} \ce{2 Fe (s) + 3/2 O2 (g) -> Fe2O3 (s)}$$ So the object 'absorbs' (and chemically binds) air oxygen and thus gains weight.


5

Of course it is. Mass doesn't magically appear out of nowhere. In the case of a tree, most of the mass is taken out of the air (the carbon from the carbon dioxide) and water (the oxygen and hydrogen).


4

A large proportion of the mass of the shuttlecock is in the rubber head, but the majority of the drag force that is experienced by the shuttlecock is exerted on the feathered part. If the shuttlecock is flying so that the symmetry axis is at an angle to the direction of motion, there will be a net torque around the centre of mass which acts to reduce this ...


4

It sounds as if your sunglasses have polarized lenses. (Most sunglass manufacturers offer both polarized and non-polarized lenses.) Polarization of light can happen in a variety of ways. There is an excellent tutorial here. Put simply, polarized sunglass lenses feature microscopic parallel "louvers" (like the slats on a window blind). These louvers ...


4

Because ice is (usually) at a lower temperature than steel. It also absorbs energy when it melts. You can calculate the amount of energy absorbed by either steel/ice with $mc \Delta T$. With ice you add an extra amount due to it melting. This yields the maximum amount of energy that can be absorbed. If you have enough steel at sufficiently low temperatures, ...


3

The color "black" is what your mind perceives when no light reaches the cones and rods in your retina or some part of your retina. There can be more than one reason that no light reaches your retina. One is that there are no sources of light in your vicinity ("darkness"). Another is that there are sources around but an object in your ...


3

I have experienced rather similar effects on several shower systems. The problem typically occurs when the mixer is working below its intended pressure or flow range. My experience is that high water pressures and flow rates are less problematic than gentle flow. Where I have fitted a shower pump, the problem has gone away. I once tried a "turbo" ...


3

These rainbows exist and our eyes do see them - they are just extremely thin, plus our brain filters out this information, but the edges of bright objects on dark background in the mirror do have a thin rainbow along them. Our eye is using this rainbow to infer the image comes from a mirror. I once saw an exhibit at a modern art museum - a seemingly black-...


3

There is an infinite number of reflections. The limitation that you notice comes from the "resolution" of your eye.* You can't see further smaller reflections with the naked eye of the same reason that you can't see, say, a bacteria with the naked eye. It is too small. That doesn't mean it is not there. Apart from size, for non-ideal mirrors the ...


3

All oxidation reactions will result in a greater mass of oxide than of the original material, due to the added oxygen in the oxide. Oxygen has mass, after all. The important part to note here though is that because of the mass of the original element(s) and the structure, the majority of the oxide falls to the surface, so its mass can be measured fairly ...


2

You are exactly right. A plant like a tree is basically a chemical machine for storing chemical energy by converting water and carbon dioxide into cellulose and other hydrocarbons, using solar energy to do the work. Mass is conserved at every step of the process. Animals then chemically convert plant matter into muscle, bone and brains (in some cases). Mass ...


2

Let me remark, that from microscopic point of view it is more common to talk about the conductance and conductivity, which are inverse to the resistance and resistivity. Thus, I might use below these terms interchangeably. Resistivity is a property of a material Within classical electrodynamics (i.e., when the averaging over a macroscopic volume is implied) ...


2

you can say that black means all the light photons are absorbed, but darkness means that there aren't any photons to absorb. How can you absorb something, if there isn't anything to absorb? Your perception of "Black" is not due to what is absorbed, but to what is emitted. Why is the absence of light black? Your human visual system registers the ...


2

If you want to find the force that you're applying, it's best experimentally like this. Ask someone to stand at the side and estimate the angle $\theta$ to the vertical, that your nephew's body makes as you spin him. Estimate this angle at the point where you're applying the force, near your hands. If you are applying a force $F$ at the angle $\theta$ the ...


2

Because the ice melts and the phase change from solid to liquid enhances the cooling of the liquid due to the energy of phase change (energy removed from the liquid to melt the ice).


2

There are several factors (temperature, specific heat, volumetric heat capacity, thermal conductivity, and latent heat of fusion for ice) to consider. See the data below for steel and ice. Their relative importance depends on exactly what your goal is (lowest final water temperature and/or time to reach that temperature), how much water, ice, and steel you ...


1

As mentioned in the comments, leave a large distance to the vehicle in front. It has the advantages of: letting the dust settle before you reach it letting you see potholes with enough warning, they do not seem to suddenly appear giving you time to stop if the vehicle in front suddenly brakes allowing you to see things ahead, e.g. a traffic queue, if you ...


1

The relative centrifugal force is defined as $RCF:=\frac{\omega^2 r}{g}$ where $\omega$, $r$ and $g=9.81 \frac{m^2}{s}$ denote the angular speed of rotation, the radius of rotation and the acceleration due to gravity at the earth's surface respectively. Assuming that the point about which the rotation occurs is the midpoint of the length $90 \; cm$, the (...


1

I take care of older people's houses. When I cleaned their windows, the water would not distribute itself over the glass in a smooth way. Many small disconnected patches were visible. After I had cleaned them, these patches had grown in size significantly. Bt they were still disconnected. That was a sign that I didn't clean them "to the bottom".


1

To me, the answer is obvious by observation. I can't do the math, but if someone would care to dope it out, here is my theory. If we eliminate designs that are specific to heat conservation, such as double walls and lids, and make it strictly a single-walled material with an open top: a mug which angles inward to a narrow neck and top from a wider bases ...


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