Lecture15

m0 v k 2 m 0 v 22 22 2 m0 v 2 m0 v k

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Unformatted text preview: condensate •  4He below 2.17 K acts as a superfluid •  Liquid displays no resistance for moUon through it. –  Zero viscosity (Youtube clip) 11 Zero viscosity liquid He below 2 K m0 ! v ! " initial velocity of ball Helium will flow without viscosity unless atoms are excited from ground state to 1st excited state. (No work done on ball by fluid.) ! ' " velocity after creates excitation In order to excite the superfluid: Energy conservaUon: 1 1 m0 v 2 ! m0 v"2 = #E 2 2 (1) Note k is NOT Boltzmann’s constant here… Momentum conservaUon: ! ! ! m0 v ! m0 v" = "k (2) k is the quanUzed momentum of a free parUcle in a box 12 Zero viscosity ! ! m0 v ! "k !2 = ( m 0 v" )...
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This document was uploaded on 02/04/2014.

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