将抛物线y=2x2向下平移1个单位,得到的抛物线是( )
A:y=2x2+1
B:y=2x2-1
C:y=2(x+1)2
D:y=2(x-1)2
—I think it is enjoyable, I sometimes have some trouble in study.
在下列实例中,不计空气阻力,机械能不守恒的是( )