题目

Jim was so badly burnt that at first they began to _____ of his life.         A. despair      B. designate     C. disappoint       D. despise 答案：A 解析: despair of (=be in despair) 对.......失望：1) Don't despair: things will get better soon. 2) He began to despair of success. 3) He despaired of being able to repair the TV set. (他对能否修好这台电视机表示失望。) designate指明, 指出, despise 轻视, 藐视。如图1-5-14所示，小球的质量为m，带电荷量为q，悬挂小球的丝线与竖直方向成θ角时，小球恰好在匀强电场中静止不动，丝线长为L.现将小球拉到悬线竖直的方向上来，则电场力做功多少?拉力至少要做多少功? 图1-5-14