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1.距河岸(看成直线)500 m处有一艘静止的船,船上的探照灯以转速n=1 r/min转动。当光束与岸边成60°角时,光束沿岸边移动的速率为()。A.52.3m/s B.69.8 m/sC.3.14×103m/s D.4.18×103m/s解析:设经△t(△t→0)光点由A点移动到B点,如图1所示。弧AC的长度l=ωd△t/sin 60°.在△t→0时,弧AC可认为是直线,且可认为AC上BC,则AB=l/sin 60°=ωd△t/sin260°,又υ=AB/△t=
1. There is a stationary ship at 500 m from the riverbank (as a straight line) and the searchlight on board rotates at a speed of n = 1 r / min. When the light beam and the shore into a 60 ° angle, the beam along the shore of the rate of movement (). A.52.3m / s B.69.8m / sC.3.14x103m / s D.4.18x103m / s Resolution: Suppose that the light spot moves from point A to point B through △ t (△ t → 0), as shown in Figure 1 As shown. Arc AC length l = ωd △ t / sin 60 ° .At △ t → 0, arc AC can be considered as a straight line, and can be considered AC BC, AB = l / sin 60 ° = ωd △ t / sin260 ° , And υ = AB / △ t =