题目

某同学做“验证机械能守恒定律”实验时不慎将一条选择好的纸带的前面一部分破坏了，测出剩下的一段纸带上的各个点间的距离，如图所示。已知打点计时器工作频率为50 Hz，重力加速度g=10 m/s2,重锤质量为M kg。则重锤通过2、5两点时重锤重力势能减少量等于       J、重锤动能的增加量等于       J、并可得出的结论是：                     。 阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。A rich man was near death and was very upset．He had worked so hard for his money 1._______ he dreamt he could take it with him to heaven．So he2._______ (pray) to God his dream would come true．An angel appeared and said no．The man begged the angel to speak to God to see 3.______ he might break the rules．The angel reappeared and said that God could permit him to take one suitcase．4.______ (excite)，the man gathered his suitcase and filled it with pure gold bars．Afterward，he died and showed up in heaven to greet St．Peter．5.______ (see) the suitcase，St．Peter said，“Hold6.______，you can’t bring that here!”The man explained that he had God’s 7._______________ (permit) . St．Peter checked it out and said，“You are right．You are allowed8._______ suitcase，but I'm supposed to check its contents9._______letting it through.” Inspecting the things that the man found too(85)precious10.______ (leave) behind, St．Peter exclaimed，“You brought pavement? As you can see , the street of heaven is made of gold!”