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1 /20 2 /20 3 /20 4 /20 5 /20 6 /20Total /100 Name: June 25, 2009 Thursday Department/School: SID: University Physics Final Examination Kuang Yaming Honors School, Nanjing University Select five out of following six problems. 1.(20 pts. ) A rod of length moves with a speed along the 0L v x -direction. The rod makes an angle0θ with the -axis. x′(a) Show that the length of the rod as measured by a stationary observer is given by ( ) [ ]2 102 2 20cos 1 θ c L L v − = . (b) Show that the angle that the rod makes with the x -axis is where (01tan tan θ γ θ−= )2 21 1 c v − = γ . 2.(20 pts.) An electron having kinetic energy makes a head on collision with a position at rest. In the collision the two particles annihilate each other into two MeV 000 . 1 = Kγ -ray photons of equal energy, each traveling at equal angles with the electron’s direction of motion, as shown in the figure. Find the energy E , momentum p and angle of emission of the γ -rays. (The electron rest mass is .) 2/ MeV 511 . c 0ep K