图 10-15 中 A 、 B 、 C 三点都在电场中,已知 AC ⊥ BC ,∠ ABC = 60 °, BC = 20cm .把一个电量 q = 10 -5 C 的正电荷从 A 移到 B ,电场力做功为零;从 B 移到 C ,电场力做功为 -1.73 × 10 -3 J ,则该电场的场强大小和方向是 [ ]
【简答题】完形填空。 'Today is the day I start the big diet (节食),' I told my wife as I raised my hand and __ 1 __, 'No chocolate today!' 'Oh, has the hospital gift shop __ 2 __ selling it?' she asked. 'No,' I ...