Physics 105, Problem Set 11Due: Friday, December 18, 2009, 3 PM.Reading:K&K Chapters 11, 12, 13 with particular emphasis on 11.3-11.5, 12, 13.1-13.3.Knight’s Chapter 36 (on E-reserves on PHY103 website) contains additional discussion ofrelativity.Problem 1.Pressure of a gas: First consider one atom of massmbouncing elasticallyinside a perfect cube of interior sizeL×L×L=V(volumeV).The atom bounceselastically of the interior walls of the cube.Assume the walls have infinite mass and areoriented perpendicular to thex,yandzaxes.When the atom bounces, the impulse isnormal to the wall that it bounces off of. The initial velocity of the atom is~v= (vx, vy, vz).(a) What is the time-averaged force that this atom exerts on a wall whose surface isperpendicular to thexaxis?Now assume that there are N1 such atoms inside the cube. The atoms may havedifferent massesmi. The directions ˆviof their velocities are random and equally likelyto point in any direction on the unit sphere. The total kinetic energy of these atoms is
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