题目

如图所示，质量为M、内间距为L的箱子静止在光滑水平面上，箱子中间有一质量为m的小物块（可视为质点），初始时小物块停在箱子正中间．现给小物块一水平向右的初速度v，小物块与箱壁N次碰撞后恰又回到箱子正中间，并与箱子保持相对静止．设碰撞过程中没有机械能损失．求： （1） 小物块与箱子相对静止后共同速度的大小； （2） 整个过程中系统产生的热量； （3） 小物块与箱子底板间的动摩擦因数．23、阅读短文，根据所读内容在文后1-10的空格里填上适当的单词或短语，每空不超过三个单词。 Everybody has lied on some occasion in life. However, compulsive（上瘾的）lying is different. A compulsive liar has no control over his lying habit. It is very uncomfortable for him to speak the truth. He lies on both major and small issues. Compulsive liars lie out of habit and even on issues where lying does not benefit them. A compulsive liar is also called a habitual liar. A compulsive liar is not nervous at times. He lies with strong self-confidence. However, you could find evidence that he is lying, which is easy because he always lies. If a person tries to speak out irrelevant details or offer explanations which aren’t necessary when he’s asked a particular question, he’s attempting to hide certain facts. Also you can look at his body language for signs of lying. If he has crossed his arms he might be hiding certain facts from you. If he is blinking（眨眼）frequently then chances are high he is lying. Another sign is he will never admit the truth even when faced with strong evidence. The consequence of compulsive lying is that no one trusts him any more. It could have far reaching consequences on his job, relationships and friends. It is a terrible cycle, which can alienate（疏远）the very people who are dear to him. The cure for this condition is that the person affected should take the initiative. He has to meet a psychologist and/ or a psychiatrist（精神病医生）. The psychiatrist will prescribe the needed medicine. The psychologist will analyze why this behavior is happening. Hypnosis（催眠）is a possible solution to this problem. Fortunately this is a treatable condition. Title：1. ________________________