A level: Kinetic Theory QuestionsQ1. A single gas molecule of mass m is moving in a rectangular box with a velocity of ux in the positive x-direction, as shown in the diagram. The molecule moves backwards and forwards in the box, striking the end faces normally and making elastic collisions. (a)
(ii) In terms of m and ux write down an expression for the change of momentum per collision with the shaded face.
(2 marks) (b) If it is assumed that the box contains N identical molecules, each of mass m, all moving parallel to the x-direction with speed ux and making elastic collisions at the ends, show that the average force, F, on the shaded face is given by F = Nmux2/Lx Force for one mlecule = rate of change of momentum of one molecule p/t = (2mux )/(2Lx/ux) p/t = mux2)/Lx
(2 marks) (c) In a better model of molecular motion in gases, molecules of mean square speed are assumed to move randomly in the box.
(5 marks) (Total 9 marks) |
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