题目

如图所示，倾角为θ的斜面上只有AB段粗糙，其余部分都光滑，AB段长为3L。有若干个相同的小方块（每个小方块视为质点）沿斜面靠在一起，但不粘接，总长为L。将它们由静止释放，释放时下端距A为2L。当下端运动到A下面距A为L/2时小方块运动的速度达到最大。则小方块与粗糙斜面的动摩擦因数为____________，小方块停止时下端与A的距离是____________。  The United States Environmental Protection Agency says only seven per cent of plastic waste in the United States is recycled each year. A new compa?ny in northern New York says it can increase that percentage. It also says it can help the United States reduce the amount of oil it imports.  The company has a machine named the "plastic-eating monster". Every hour,thousands of kilograms of milk jugs,water bottles,and grocery bags are fed into the machine. The plastic waste comes from landfills across the United States. John Bordnyniuk runs the company,called JBI.  Mr Bordnyniuk has invented a new process for turning plastic into fuel. First,many different kinds of unwashed plastics are melted together.Mr Bordnyniuk uses a special chemical to turn the liquid into a vapour. This reduces the plastic to its most basic elements.  "Plastics are just long hydrocarbon chains. What we're doing is reforming them into links and chains that we want so they have a high fuel value.” Eight per cent of the recycled plastic is used to run the system. Independ?ent testers say eighty-six per cent of what goes in comes out as fuel.  Bob Molodynia helps run the company. He watches as the plastic-eating machine pours a thin,brown liquid into an oil barrel.  JBI produces several thousand liters of fuel a day. It creates different grades of fuel for different industries. It sells the fuel for up to one hundred dollars a barrel. Each barrel costs about ten dollars to produce.  Scientists say plastic-to-oil technology is still new and developing. They say it is not yet known if the process is environmentally friendly. And some questions whether turning plastic into oil can even be considered "recycling".  Carson Maxted is with the publication Resource Recycling,a magazine that reports on the plastic recycling industry. He says because there is a lot of plastic waste and a great demand for oil,JBFs recycling technology may create great changes in both industries.1. What should be the best title of the passage?   A. Could waste plastic reduce our need for oil?   B. How can waste plastic be changed into oil?   C. What should we do to reduce the import of oil?   D. What is the "plastic-eating monster"?2. What is the purpose of using a special chemical?   A. To melt the unwanted plastic.   B. To turn liquid plastic into vapour.   C. To turn plastic into fuel.   D. To make the machine use more plastic.3. From the passage,we know      .   A. there is a great profit for JBI to turn waste plastic to oil   B. plastic-to-oil technology is very developed in America   C. the process of turning plastic into fuel is environmentally friendly   D. JBI's recycling technology must create great changes in the plastic re?cycling industry4. Who is the boss of JBI?   A. Carson Maxted.   B. John Bordnyniuk.   C. Bob Molodynia.   D. Machiel Smiths.