【題目】如圖所示，A、B兩球質(zhì)量相等，光滑斜面的傾角為，圖甲中，A、B兩球用輕彈簧相連，圖乙中A、B兩球用輕質(zhì)桿相連，系統(tǒng)靜止時(shí)，擋板C與斜面垂直，彈簧、輕桿均與斜面平行，則在突然撤去擋板的瞬間有（ ）

A．兩圖中兩球的加速度均為

B．兩圖中A球的加速度均為零

C．圖乙中輕桿的作用力一定不為零

D．圖甲中B球的加速度是圖乙中B球加速度的2倍

【答案】D

【解析】當(dāng)撤去擋板時(shí)，甲圖中由于彈簧的壓縮量不能突變，A球還會(huì)受到不變的彈力作用，能繼續(xù)平衡；而B球沿斜面方向受到重力分力mgsin和彈簧彈力mgsin兩個(gè)力，所以B球會(huì)產(chǎn)生2gsin加速度。乙圖中輕桿的形變很小，撤掉擋板后，輕桿的彈力可以發(fā)生突變。將A、B看成整體可知，A、B會(huì)沿斜面以gsin加速度下滑，可知輕桿的彈力瞬間消失。綜上所述，選項(xiàng)D正確。

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