【单选题】如图所示,一个质量为 m 、电荷量为 q 的带电小球从 M 点自由下落。 M 点距场区边界 PQ 高为 h ,边界 PQ 下方有方向竖直向下、电场强度为 E 的匀强电场,同时还有垂直于纸面的匀强磁场。小球从边界上的 a 点进入复合场后,恰能做匀速圆周运动,并从边界上的 b 点穿出。重力加速度为 g ,不计空气阻力,则下列说法中正确的是 ( ) 。
【简答题】Unit 2 Passage A Dog talk: Every dog has its day Americans have many expressions using the word “dog.” Nowadays people in the United States love their dogs and treat them well. They take their dogs fo...
【简答题】Americans have many expressions ___(used, using) the word “dogs”. Nowadays people in the United States love their dogs and ______(threat, treat)them well. They take their dogs ____(for , on ) walks,l...
【简答题】Scientists have reached the conclusion _____ the temperature on the earth is getting higher and higher . A.what B. that C.it D. because 2. I’m not _____ to think I can succeed without efforts . A.n...
【简答题】l Dog talk: Every dog has its day Americans have many expressions using the word “dog.” Nowadays people in the United States love their dog and treat them well. They take their dogs for walks, let the...