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19

Depending on the angle of the sun, the shadow becomes elongated so that it traces out an ellipse rather than a circle. This means that the shadows of the blades must traverse a different distance across the ground but within the same time period, thus giving rise to the periodic variation in velocity. If the sun is at an angle $\alpha$ in the sky (see the ...


1

EDIT: The "old" explanation below is quite informal, as gravity cannot produce a torque around the center of mass. See the new explanation below it. Humans lean forwards slightly as they run (more so if they run faster, and have to counter larger drag forces). This makes gravity exert a counter-torque that exactly balances the torque produced by action of ...


1

Light from the source is emitted in all directions - including towards every point on the road surface. When the light hits the (wet, rough) surface of the road, it is scattered in a variety of angles. Some of the light rays will be scattered at just the right angle to enter your eye. Therefore reflected light from all different parts of the road between ...


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Short answer: plasma ball emits RF "noise". The touch screen is sensitive to noise (as it tries to detect the presence of your finger by detecting very tiny currents that appear between transparent electrodes as a result of the presence of your finger (which is dielectrically different than air ). Hoping someone else will elaborate for you.


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The cited diagram depicts but a small part of the motions that occur during a dive. That appears to be an overly simplified diagram of a rather simple springboard dive, a forward 1 1/2 somersault tuck. It's overly simplified because it misses the complex motions a diver undergoes at the start of the dive. There are two mechanisms by which a diver turns ...


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Also, at lower temperatures the air cannot hold as much water vapor so lower temperatures may not feel as cold as higher temperatures.


5

Earbud cords form coils in your pocket. Even if you crumple the cord, it eventually finds its way into coils as you move and the cord is agitated. The coils lie in planes that are stacked. It's been found that agitated coils spontaneously braid and knot themselves. See this paper: http://www.pnas.org/content/104/42/16432.full, which found that formation ...


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Take an empirical approach; go to a oil-change place. Put the car up on a rack/lift (the kind that supports the frame, not the tires - allows tire rotation during oil change). Have them adjust tire pressure while car is up in the air; have them remeasure when the car is back on the ground (tell them why - give them "scientist for a day" certificate). Because ...


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It certainly affects life expectancy and if do it continuously at right intervals you can even destroy the motor/generator in a matter of few minutes: http://en.wikipedia.org/wiki/Aurora_Generator_Test When a motor/generator is connected to the grid it revolves in-phase with the grid. When you disconnect it, its frequency will change and its phase will ...


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As an illustration of Dan's answer I get myself a diffraction grating and start looking at florescent lamps. I was frankly really disappointed because you really don't get to see the lines clearly with a grating alone. What you would see is more or less like this But I moved on and told myself that I can make myself a spectroscope and I did just that! I ...


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The two lenses in modern 3D glasses are designed to select the two circular polarizations. The left lens only transmits left-circularly polarized light and the right lens only transmits right-circularly polarized light (or vice versa). The problem is that there is no material which acts as a circular polarization filter on its own. The way in which they ...


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Most of the masks work on the principle of adsorption. This is a surface phenomenon where particles stick to the surface of another material called adsorbent. Most commonly used material is activated charcoal. When used is a smelly environment, the particles/molecules responsible for the smell are filtered first (this happens only for larger particles) and ...


3

The can is acting as a compact heat pipe. When you grasp the can, the liquified gas inside the can absorbs the heat from your hand and expands, carrying the heat away in convective currents that dissipate the heat to other parts of the surface that are at a lower temperature than your hand. Since it draws heat from your hand it feels cool to the touch.



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