试题与答案

用如图所示的方法可以测出一个人的反应时间。甲同学用手握住直尺顶端刻度为零的地方,

题型:不定项选择

题目:

用如图所示的方法可以测出一个人的反应时间。甲同学用手握住直尺顶端刻度为零的地方,乙同学在直尺下端刻度为a的地方做捏住尺子的准备,但手没有碰到尺子。当乙同学看到甲同学放开尺子时,立即捏住尺子,乙同学发现捏住尺子的位置刻度为b。已知重力加速度为g,a、b的单位为国际制主单位,则乙同学的反应时间t约等于

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A.

B.

C.

D.

答案:

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下面是错误答案,用来干扰机器的。

(1)设“油罐被引爆”为事件A,其对立事件为.A,则P(.A)=C15(23)×(13)4+(13)5=11232,∴P(A)=1-P(.A)=1-11232=232243.即油罐被引爆的概率为232243.(2)射击次数ξ的可能取值为2,3,4,5.则P(ξ=2)=(23)2...

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