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The legs of water beetles have little hairs which spread out to catch and move water back in the power stroke, but lay flat as the appendage moves forward in the return stroke. Also, one side of a water beetle leg is wider than the others and is held perpendicular to the motion when pushing backward, but the leg rotates when the limb returns ...
The vector forces exerted on the water by such motion cancel out laterally, but generate a net force backwards which in turn pushes the fish forward through the water. Most fishes generate thrust using lateral movements of their body and caudal fin , but many other species move mainly using their median and paired fins.
Since air temperature and composition varies significantly with altitude, the speed of sound, and Mach numbers for a steadily moving object may change. In water at room temperature supersonic speed means any speed greater than 1,440 m/s (4,724 ft/s). In solids, sound waves can be polarized longitudinally or transversely and have higher velocities.
Photons interact with an object by some combination of reflection, absorption and transmission. Some materials, such as plate glass and clean water, transmit much of the light that falls on them and reflect little of it; such materials are called optically transparent. Many liquids and aqueous solutions are highly transparent.
Anglers off the coast of Taiwan recently reeled in a peculiar kind of fish — with translucent fins and bulging eyes — from deep below the surface.
The fluid pressure behind the object is lowered below the vapour pressure of the liquid, forming a bubble of vapour (a cavity) that encompasses the object and reduces drag. Supercavitation is the use of a cavitation bubble to reduce skin friction drag on a submerged object and enable high speeds .
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 °C, 32 °F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a mineral.
Some draperies are translucent, and some have brown and beige layers that look much like bacon (often termed "cave bacon"). Though flowstones are among the largest of speleothems, they can still be damaged by a single touch. The oil from human fingers causes the flowing water to avoid the area, which then dries out. Flowstones are also good ...