A.Private Sub Form. Load() Show Text1.Text=" " Text2.Text=" " Text2.SetFocus End Sub Private Sub Text2_KeyDown(KeyCode As Integer,Shift As Integer) Text1.Text=Chr(KeyCode-4) End Sub
B.Private Sub Form_Load() Show Text1.Text=" " Text2.Text=" " Text2.SetFocus End Sub Private Sub Text2_KeyDown(KeyCode As Integer,Shift As Integer) Text1.Text=Text1.Text+Chr(KeyCode-4) End Sub
C.Private Sub Form_Load() Show Text1.Text=" " Text2.Text=" " Text2.SetFocus End Sub Private Sub Text2_Click(KeyCode As Integer,Shift As Integer) Text1.Text=Text1.Text+Chr(KeyCOde-4) End Sub
D.Private Sub Form_Load() Show Text1.Text=" " Text2.Text=" " Text2.SetFocus End Sub Private Sub Text2_Click(KeyCode As Integer,Shift As Integer) Text1.Text=Chr(KeyCode-4) End Sub
的线速度比下部的质点B的线速度大,因而通过黏性力带动的空气流动的速度也大,根据伯努利原理,球下面的压强较上面大,从而受到向上的升力。这结论和书上的相反,怎么回事?
一正弦形式空气波沿直径为14cm的圆柱形管行进,波的平均强度为,频率为300Hz,波速为300m/s。问波中的平均能量密度和最大能量密度各是多少?每两个相邻同相面间的波段中含有多少能量?