【简答题】A—Sold B—For sale C—All sold out today D—Bargain sale E—Not for sale F—Be ware of picking pockets G—Closed H—House to let I—Emergency exit J—Pr fire K—Lavatory L—Closed to all vehicles M—Keep rig...
【单选题】如图所示,两根平行光滑导轨竖直放置,相距 L = 0.1 m ,处于垂直轨道平面的匀强磁场中,磁感应强度 B = 10 T ,质量 m = 0.1 kg ,电阻为 R = 2 Ω 的金属杆 ab 接在 两导轨间,在开关 S 断开时让 ab 自由下落, ab 下落 过程中、始终保持与导轨垂直并与之接触良好,设导轨足够长且电阻不计,取 g = 10 m /s 2 ,当下落 h = 0.8 m 时,开关...