【題目】我國(guó)發(fā)射的宇宙飛船在完成任務(wù)后，返回地面指定地點(diǎn)，宇宙飛船在下落到地面附近時(shí)，由于空氣阻力作用做勻速直線運(yùn)動(dòng)，則宇宙飛船在勻速下降的過(guò)程中，它的（�。�

A.動(dòng)能不變，勢(shì)能減小，內(nèi)能增大　　　

B.動(dòng)能不變，勢(shì)能增大，內(nèi)能減小

C.動(dòng)能減小，勢(shì)能不變，內(nèi)能增大　　　

D.動(dòng)能增大，勢(shì)能減小，內(nèi)能不變

【答案】A

【解析】試題分析: 我國(guó)發(fā)射的宇宙飛船在完成任務(wù)后，返回地面指定地點(diǎn)，宇宙飛船在下落到地面附近時(shí)，由于空氣阻力作用做勻速直線運(yùn)動(dòng)，則宇宙飛船在勻速下降的過(guò)程中，由于它是勻速運(yùn)動(dòng)的所以，動(dòng)能是不變的。飛船的高度在減小，所以勢(shì)能變小。飛船和空氣有摩擦，在下落的過(guò)程中機(jī)械能會(huì)轉(zhuǎn)化為內(nèi)能。

A.動(dòng)能不變，勢(shì)能減小，內(nèi)能增大　　　符合題意；

B.動(dòng)能不變，勢(shì)能增大，內(nèi)能減小 不合題意；

C.動(dòng)能減小，勢(shì)能不變，內(nèi)能增大　　　不合題意；

D.動(dòng)能增大，勢(shì)能減小，內(nèi)能不變 不合題意；

故選A。

考點(diǎn):本試題考查的是機(jī)械能的轉(zhuǎn)化。動(dòng)能是物體由于運(yùn)動(dòng)而具有的能量，動(dòng)能跟物體的質(zhì)量和物體運(yùn)動(dòng)的速度有關(guān)。勢(shì)能跟物體的質(zhì)量和物體被提升的高度有關(guān)。

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