用原长为15cm的弹簧竖直吊起一块木块,稳定后弹簧长23cm,用这弹簧在水平桌面上水平匀速拉动该木块,弹簧的长为17cm,求木块与桌面间的动摩擦因数.
我国下列省级行政区中,受寒潮影响较小的是 ( )
- When is Lang Lang's concert?
- It's three o'clock the afternoon of December 18th.