题目

某实验小组设计了如图(a)所示的实验装置，通过改变重物的质量，利用计算机可得滑块运动的加速度a和所受拉力F的关系图象．他们在轨道水平和倾斜的两种情况下分别做了实验，得到了两条a—F图线，如图(b)所示．滑块和位移传感器发射部分的总质量m=_____kg；滑块和轨道间的动摩擦因数μ=_________．(重力加速度g取10 m/s2)  39、Every person leaves a footprint. That’s what I learnt when I started to work as a private investigator 10 years ago. People pay restaurant bills with their bank card, check into hotels                or travel around. In every case, they leave a trace. And because of this, I’m able to track them down even when they don’t want to be found. The first thing I do when I want to find out where someone is staying is to go to the neighbourhood where he used to live. It’s human nature to tell stories — which is why neighbours will tell me all they know when I ring at their houses. Sometimes, someone even talks about his friend’s dishonesty. Then I produce a pattern of my subject’s life: if he likes to have a holiday in Spain or in Italy, if he prefers two or three-star hotels and where he might hide his assets （资产）. When I’ve got this life pattern, I start my research. Nine times out of 10, I find the people I’m looking for. I once investigated a lorry supplier who owed ?500,000 to a subcontractor （分包商）. The subcontractor wanted to find out if it was worth bringing charges against the supplier. I found out the supplier had moved assets to his son, who founded a new company offering the same product. It was all done within the law. There was no money to be got from that operation. However, I asked the son if I could speak to his father and he told me that his parent was on a long holiday in Spain and wouldn’t be back for a while. It didn’t take me long to find out that the father wasn’t in Spain. I went back to the son and this time he told me that his father might in Bulgaria, and I found him doing winter sports in a beautiful mountain area. He was living in a big house on a large piece of land he had bought for ,000. This was exactly the kind of asset my customer was looking for. 1．We learn from the text that a private investigator is one who         .   A．follows people and reports on what they do   B．helps people start businesses   C．gives advice to people about the law   D．settles arguments between companies 2．Why does the author visit the place where his subject used to stay?   A．To find out his hidden assets．          B．To gather information about him.   C．To discover why he is dishonest．       D．To find out where he spends his holiday. 3．The lorry supplier moved his assets to his son in order to ________   A．pass on his debt to his son   B．double the business of his company   C．let his son take over his lorry business      D．prevent paying back the money he owed 4．We may infer from the text that the subcontractor might _________   A．bring charges against the lorry supplier’s son       B．give up hope of settling the debt   C．sell the big house in Bulgaria   D．get his money back