题干

2009年2月11日,俄罗斯的“宇宙-2251”卫星和美国的“铱-33”卫星在西伯利亚上空约805km处发生碰撞。这是历史上首次发生的完整在轨卫星碰撞事件。碰撞过程中产生的大量碎片可能会影响太空环境。假定有甲、乙两块碎片,绕地球运动的轨道都是圆,甲的运行速率比乙的大,则下列说法中正确的是

A:甲的运行周期一定比乙的长

B:甲距地面的高度一定比乙的高

C:甲的向心力一定比乙的大

D:甲的加速度一定比乙的大

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答案(点此获取答案解析)

D

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    Two young giant-panda twins born in the United States have returned home to China, but are straggling to adapt to the language and food.

    The 3-year-old sisters, Mei Lun and Mei Huan, wens the first surviving panda twins to be born in the United States, and were returned to China from Zoo Atlanta on Nov. 5. But the pair still understand English belter than Chinese, and prefer American biscuits to Chinese bread.

    A zoo-keeper said that his main concern is that the pair are so addicted to American biscuits that everything they eat — from bamboos to apples — has to be mixed with biscuits. They even want to snack on (零食) biscuits when drinking water.

    The zoo -keeper is trying to wean them off their biscuit habit, gradually replacing the American food with Chinese bread. Mei Huan is adapting, but Mei Lun doesn't want to touch the unfamiliar bread.

    Mei Lun is the livelier of the two, often jumping onto the roof and hanging upside down from a rail, but her slightly younger sister Mei Huan is calmer, preferring to sit still, observe her new environment and occasionally snack on bamboo.

    A language barrier is also reported. While the pair respond to their own names, and understand some English phrases such as “come here,” they don't understand the Sichuan dialect of Chinese.

    The news caused some laughter on Chinese social media, with some users commenting that the pandas would soon get used to Sichuan's famously spicy cuisine.