[题目] “神州二号无人飞船环绕地球108圈.顺利完成预定空间科学试验任务后.于2001愿军年1月16日在内蒙古中部准确返回.成功着陆.标志着我国载人航天工程第二次飞行实验取得圆满成功.若飞船穿越大气层时.有一段为匀速降落过程.则在此过程中飞船的( )A．动能减小.机械能增大 B．动能不变.机械能减小C．动能增大.机械能减小 D．动能题目和参考答案——青夏教育精英家教网—

题目内容

【题目】 “神州二号”无人飞船环绕地球108圈，顺利完成预定空间科学试验任务后，于2001愿军年1月16日在内蒙古中部准确返回，成功着陆，标志着我国载人航天工程第二次飞行实验取得圆满成功，若飞船穿越大气层时，有一段为匀速降落过程，则在此过程中飞船的（）

A．动能减小，机械能增大 B．动能不变，机械能减小

C．动能增大，机械能减小 D．动能减小，机械能不变

【答案】B

【解析】

试题分析：动能大小的影响因素：物体的质量、物体的速度，质量越大，速度越大，动能越大；

重力势能大小的影响因素：物体的质量、物体的高度，质量越大，所处的位置越高，重力势能越大；

动能和势能统称为机械能．

解：当飞船匀速降落时，飞船的质量不变、速度不变，动能不变；飞船的质量不变，高度越来越小，重力势能越来越小，机械能减小．

故选B．

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