(2) F= qob Le。（a2+b2）3/2 由 oF= qOb O 0bLe(a2+b2)32 品a46pa-0 ao a 得到： b22 =0.07m 题号结束 π q ε0 Q ( ) b 2 a + 2 b = 3 2  b =0 b a = 2 得到: =0.07m π q ε0 Q ( ) = b 2 a + 2 b 3 2 F (2) F b π q ε0 Q ( ) b 2 a + 2 b = 3 2  b 由 题号 结束