There's a reason why disk brakes are better than V brakes on a mountain bike and it has nothing to do with the usual arguments: no mud and no water reaches the disks thus the braking is more efficient - unlike the rims which easily gather mud, sand and water while crossing streams, making it harder for the cyclist to stop the bike (not only that but the brake pads and the rims themselves are worn out by the abrasive materials caught between them, which not cool...).
|The same physics law that makes the rim of the wheel move faster than any point situated closer to the center of the wheel is responsible for the noise of the helicopter rotor blade. Some of the noise that we hear in a flying helicopter (bang bang bang) is a series of sonic bangs caused by the tips of the blade which travel through air at supersonic speeds. The longer the blade, the faster the speed of its tip (rotations per minute being constant). Military forces are working to reduce this noise for stealth operations -|
long-range propagation of helicopter noise can alert an enemy to an incoming helicopter in time to re-orient defenses.Read more about helicopter noise reduction and rotor noise (see page 4).
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