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问题 选择题

—What can I do for you ?     —I want            . [ ]

A. a glass of oranges

B. two bottles of milk

C. two bags of salts

答案

答案：B

计算题

两平行金属板A、B水平放置，一个质量m=5×10-6kg的带电微粒以υ0=2m/s的水平初速度从两板正中央位置射入电场，如图所示，A、B两板间的距离d=4cm，板长L=10cm。

（１）当A、B间的电压UAB=1000V时，微粒恰好不偏转，沿图中直线射出电场，求该粒子的电量。

（２）令B板为电势零点，A板电势高于B板电势，欲使该微粒射出偏转电场，求AB板电势差的最大值和最小值。

　
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问答题

Exercise, everyone advises! But immediately, when you try, you run into trouble. (46)There is so much contradictory, sometimes incorrect advice about exercising that you become confused. Test yourself on the following true false quiz. It will tell you what you need to know.
1. The best way to reduce the mid-section is to do abdominal exercise.
False. Many people believe that when specific muscles are exercised, the fatty tissues in the immediate area are "burned up." (47)The truth-is that exercise burns fat from all over the body and not from one specific area, regardless of the type of exercise. Of course, if you reduce the fat throughout your body, you will certainly see results around your waistline too!
2. To maintain an adequate level of physical fitness, you need to exercise only twice a week.
False. Studies conducted by NASA, the National Aeronautics and Space Administration, show that unexercised muscles lose their strength very quickly. After 48 to 72 hours, you must use the muscles again to reestablish the good physical effect. And what does that mean to you (48) NASA scientists concluded that while daily exercise is most beneficial, three alternating days each week will maintain an adequate level of physical fitness.
3. To lose weight you should always "work up a good sweat" when exercising.
False. Sweating only lowers body temperature to prevent overheating; it does not help you reduce weight. You may weigh less immediately after a workout, but this is due to water loss. Once you replace the liquid, you replace the weight.
4. If your breathing doesn’t return to normal within minutes after you finish exercising, you’ve exercised too much.
True. Five minutes or so after exercising, your breathing should be normal, your heart shouldn’t be pounding, and you shouldn’t be exhausted. (49) Beneficial exercise is not overly difficult, unpleasant, and exhausting; it is moderate, enjoyable, and refreshing.
5. Walking is one of the best exercises.
True. Walking helps circulation of blood throughout the body, and thus has a direct effect or your overall feeling of health.
6. The minimum amount of time you should spend exercising in a day is 20 minutes.
True. There are more than 400 muscles that attach to your skeleton. (50) A good exercise routine should contract and stretch all these muscles, and this simply cannot be done with four or five exercises in five to ten minutes. From experience, I’ve found that about 20 minutes is the minimum amount of time needed for an adequate workout.
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