89. (Third problem ofCluster)(a) By momentum conservation we see that their Fnal speeds are the same. We use energy conservation(where the “Fnal” subscript refers to when they are inFnitely far away from each other):Ui=Kf14πε02Q2D=2µ12mv2¶which (usingk=1/40) yieldsv=|Q|r2kmD.(b) As noted above, this result is the same as that of part (a).(c) We use energy conservation (where the “Fnal” subscript refers to when their surfaces have madecontact):Ui=Kf+Uf140−2Q2Dµ12mv2¶+140−2Q22rwhich (usingk/40) yieldsv=|Q|rkmr−
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This note was uploaded on 11/12/2011 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.