如图所示，导体框架的平行导轨（足够长）间 距d=lm，框架平面与水平面夹角θ=37°，框架的电阻不计，电阻R₁=0.4Ω．匀强磁场方向垂直框架平面向上，且B=0.2T，光滑导体棒的质量m=0.2kg，电阻R=0.1Ω，水平跨在导轨上，由静止释放，g取 10m/s²，sin37°=0.6，cos37°=0.8，求：

      It's never easy to admit（承认）you are in the wrong. We all 1 to know the art of apology（道歉）. Think how often you've done wrong. Then count how many 2 you've expressed clearly you were 3 . You can’t go to bed with an easy mind if you do 4 about it.
      A doctor friend, Mr Lieb, told me about a man who came to him with different kinds of signs: headaches, heart trouble and insomnia（失眠症）. 5 some careful exams, Mr Lieb found nothing wrong with him and said, “If you don't tell me what's 6 you, I can't help you”.
      The man admitted he was cheating（骗取） his brother of his inheritance（遗产）. Then and there the clever doctor 7 the man write to his brother and8 his money. As soon as the letter was put into the post box, the man suddenly cried.“Thank you ,” he said to the doctor, “I think I've got well.”
      An apology can not only save a broken relationship（关系）, but also make it9 . If you can think of someone who should be 10an apology from you, do something about in right now.

金属钛及钛的合金被认为是21世纪重要的金属材料，地壳中的钛矿石主要是金红石（TiO₂），TiO₂中钛的化合价是____ ．目前工业上制取钛的方法是：第一步，在高温时，将金红石、炭粉混合并通入氯气（Cl₂）制得TiCl₄和一种可燃性气体，该反应的化学方程式是____ ；第二步，在氩气的环境中，用过量的金属镁在加热条件下与TiCl₄反应制得金属钛（氩气不参加反应），该反应的化学方程式是：____ ．工程技术人员常用铝和氧化铁在高温条件反应生成氧化铝和铁来焊接铁轨间的缝隙，化学方程式是　____ ．

饲养观赏鱼，可以陶冶人的情操，增进人们对生活的热爱．空运观赏鱼，必须密封．为了解决鱼的吸氧问题，可在水中加入过氧化钙（化学式CaO₂），过氧化钙与水反应生成的是氢氧化钙和氧气．写出过氧化钙与水反应的化学方程式　____ ．