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Can a bullet go faster in water than in air--- I have been told that & I dont think its logical
You are thinking logically when you say that bullets should not be able
to travel faster in water than in air. In most cases any projectile
entering the water will be slowed down by drag. This we know from
jumping into a swimming pool. However there is a special case known as
supercavitation which involves powerful torpedoes that are able to
travel at super speeds beneath the water surface with minimal drag. The
key to supercavitation is creating an object (bullet, torpedo) with a
nose specially shaped and firing at a very high velocity so that it
creates a low pressure zone around the entire object. At this high
velocity the water will flow off the nose at angles preventing it from
wrapping around the projectile and creating drag. The low pressure
bubble that is created around the object will allow the object to
reside in a vapor cavity. Drag is proportional to the density of the
surrounding fluid therefore because this proportion is smaller due to
the low pressure and vapor cavity, there will be reduced drag and the
object will be able to continue at super fast speeds.
(republished on 07/30/06)
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