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某个热气球充气后体积为3000m3，则该热气球所受的浮力为____N．（g取10N/kg，空气的密度取1.29kg/m3）．

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解析：
浮力公式F浮＝ρ液V排同样适用于气体，即F浮＝ρ气V排＝1.29kg/m3×10N/kg×3000m3＝3.87×104N．
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