题干

在交通事故的分析中,刹车线的长度是很重要的依据。在某次交通事故中,交通警察测量出肇事车辆的刹车痕迹是30米,该车辆最大刹车加速度是15m/s2,该路段的限速50km/h。则该车是否超速(     )

A:超速

B:不超速

C:无法判断

D:刚好是50km/h

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答案(点此获取答案解析)

A

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阅读理解

    Chokwe Selassie, aged 13, is working hard to help drivers avoid potholes(坑洼). The eighth-grader was inspired to kick off his creation on a recent morning, when his mother was driving him to school. Their car was damaged as it went over a huge pothole in the middle of the street in their hometown of Jackson, Mississippi. He decided to do something about the pothole problem in his city. His solution: an app that warns drivers when there is a pothole ahead.

    Chokwe developed the app with his friends Rodriguez Ratliff and Emmanuel Brooks. When the app detects a pothole, it is highlighted in red. And if you get close to the pothole, your phone will warn you. Drivers can also use the app to report any potholes they meet, and to look for other routes they can take to avoid roads that have them.

    The app relies on current available information about the streets of Jackson. It works by using the city's 311 call system, and uses information already stored in a database. Through the call system, citizens dial 311 to report non-emergency problems, which include potholes. Chokwe and his friends determined that focusing on the 10 busiest streets in Jackson would give them a large enough sample size to test the prototype(原型).

    Although the app isn't yet available for sale,Chokwe is already looking for ways to improve it. The prototype remains limited to 10 streets in Jackson, but he hopes to add more, so that it includes every street in the city. And then he wants to go even farther until it's nationwide.