1、(2009年全國卷Ⅰ)19．天文學家新發(fā)現(xiàn)了太陽系外的一顆行星。這顆行星的體積是地球的4.7倍，質(zhì)量是地球的25倍，已知某一近地衛(wèi)星繞地球運動的周期約為1.4小時，引力常量G=6.67×10^-11N·m²/kg²，由此佑算該行星的平均密度約為

A．1.8×10³kg/m³　　 B．5.6×10³kg/m³　　 C．1.1×10⁴kg/m³　　 D．2.9×10⁴kg/m³

答案D

[解析]本題考查天體運動的知識.首先根據(jù)近地衛(wèi)星饒地球運動的向心力由萬有引力提供,可求出地球的質(zhì)量.然后根據(jù),可得該行星的密度約為2.9×10⁴kg/m³

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