Velocity - <span><span>the speed of something in a given direction
Speed - </span></span><span>rapidity in moving, going, traveling, proceeding, or performing; swiftness; <span>celerity
Velocity is the speed in a certain direction, whereas speed is just the rate of fastness.
Does that make sense?
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The point at which all motion stops.
You get a more low sound.
Conversely, when the wavelength becomes shorter you get a more treble sound.
;-)
C is the answer to your question.