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【题目】我国发射的宇宙飞船在完成任务后,返回地面指定地点,宇宙飞船在下落到地面附近时,由于空气阻力作用做匀速直线运动,则宇宙飞船在匀速下降的过程中,它的( )

A.动能不变,势能减小,内能增大   

B.动能不变,势能增大,内能减小

C.动能减小,势能不变,内能增大   

D.动能增大,势能减小,内能不变

【答案】A

【解析】试题分析: 我国发射的宇宙飞船在完成任务后,返回地面指定地点,宇宙飞船在下落到地面附近时,由于空气阻力作用做匀速直线运动,则宇宙飞船在匀速下降的过程中,由于它是匀速运动的所以,动能是不变的。飞船的高度在减小,所以势能变小。飞船和空气有摩擦,在下落的过程中机械能会转化为内能。

A.动能不变,势能减小,内能增大   符合题意;

B.动能不变,势能增大,内能减小 不合题意;

C.动能减小,势能不变,内能增大   不合题意;

D.动能增大,势能减小,内能不变 不合题意;

故选A

考点:本试题考查的是机械能的转化。动能是物体由于运动而具有的能量,动能跟物体的质量和物体运动的速度有关。势能跟物体的质量和物体被提升的高度有关。

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