106_Physics ProblemsTechnical Physics

106_Physics ProblemsTechnical Physics - Chapter 4 *P4.60...

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Chapter 4 107 *P4.60 (a) We use the approximation mentioned in the problem. The time to travel 200 m horizontally is t x v x == = 200 1000 0200 m ms s , . . The bullet falls by yv t a t yi y =+ = + = 1 2 0 1 2 98 02 0196 2 2 .. . s m 2 ej a f . (b) The telescope axis must point below the barrel axis by θ ° tan . . 1 200 00561 m m . (c) t 50 0 00500 . . m s . The bullet falls by only y =− = 1 2 005 00122 2 . s m 2 a f . 50 150 200 250 barrel axis bullet path scope axis FIG. P4.60(b) At range 50 1 4 200 m m = a f , the scope axis points to a location 1 4 19 6 4 90 cm cm a f = above the barrel axis, so the sharpshooter must aim low by 490 122 368 . cm cm cm −= . (d) t y = 150 0150 1 2 015 0110 2 m s s m 2 . . a f Aim low by 150 200 19 6 11 0 3 68 ... cm cm cm af . (e) t y = 250 0250 1 2 025 0306 2 m s s m 2 . . a f Aim high by 30 6 250 200 19 6 6 cm cm .12 cm . (f), (g) Many marksmen have a hard time believing it, but they should aim low in both cases. As in case (a) above, the time of flight is very nearly 0.200 s and the bullet falls below the barrel axis by 19.6 cm on its way. The
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