则有:mω2r=Mω2R
又由已知:r+R=L
解得: R=mm+
如图所示,在平行金属带电极板MN电场中将电荷量为﹣4×10﹣6C的点电荷从A点移到M板,电场力做负功8×10﹣4 J,把该点电荷从A点移到N板,电场力做正功为4×10﹣4J,N板接地,设地面为零势面.则
—_____, madam, but if you want good quality, you have to pay for it.