将铅直运动方程无量纲化，试由此方程分析取静力平衡近似的条件为

<p> 以静止的基本状态为背景的铅直运动方程为，<br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/2014101318305064459.jpg"><br> <br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/201410131830289215.jpg"><br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/2014101318313032917.jpg"><br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/2014101318330716063.jpg"><br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/2014101318331815192.jpg"><br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/2014101318335654350.jpg"><br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/2014101318340349562.jpg"><br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/2014101318342346987.jpg"></p>