题干

图中给出某一通关游戏的示意图,安装在轨道AB上可上下移动的弹射器,能水平射出速度大小可调节的弹丸,弹丸射出口在B点的正上方,竖直面内的半圆弧BCD的半径为R=2.0m,直径BD水平且与轨道AB处在同一竖直平面内,小孔P和圆心O连线与水平方向夹角为37º,游戏要求弹丸垂直于P点圆弧切线方向射入小孔P就能进入下一关.为了能通关,弹射器离B点的高度和弹丸射出的初速度分别是(  )(不计空气阻力)

A:0.15m,43m/s

B:1.50m,43m/s

C:0.15m,26m/s

D:1.50m,26m/s

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答案(点此获取答案解析)

A

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阅读理解

    The bike-sharing companies that are powering a transportation revolution in China's urban centers are not like those in the rest of the world. Their bikes have no docking ports or assigned zones for parking. Instead, riders open their smartphone apps, hop on, and start riding. So easy!

    In 2015, Ofo, China's bike-share pioneer, launched its first fleet of bicycles in Beijing. The bikes' bright yellow frames were soon met by the orange-rimmed(镶边), basket-equipped models launched by Mobike, Ofo's main competitor today. In little over a year, the two companies have had a huge impact on revitalizing (重振) cycling in China, particularly among young people.

    Ofo placed 1 million bicycles across 35 cities and registered 15 million users in its first years, while Mobike has now gained more than 10 million unique users and bicycles in 21 cities. Inspired by their success, at least 10 other companies have jumped into the market, launching their own app-powered, brightly colored bikes in quick succession. But Mobike and Ofo are far ahead of them.

    The two industry leaders each take a different marketing method to a similar product. The Mobike app uses GPS to display bikes' locations to users. They can use the map to reserve a bike and walk over to it. A scan of the bike's QR code (二维码) unlocks the bike, and when users manually(手动地) lock the bike at the end of their trip, the app records the trip's end and the bike will pop back up on the map as available. Equipped with this wireless technology, Mobikes cost between 1,000 and 3,000 yuan. Rides cost 1 yuan for an hour or a half hour, depending on whether a user chooses a “Lite” or regular bike, and the deposit (押金) required to the service is 299 yuan.

    Ofo, meanwhile, is devoted not just to producing its own bikes, which have slim yellow bodies and cost about 250 yuan, but also to connecting existing bikes to its network----- a philosophy that begins with the practice of 2000 bikes offered to a campus bike-share program. The 2000 bikes were the first generation of Ofo. Yet the majority of the company's bikes are currently ones that have been specially manufactured and fitted with their lock system. Unlike Mobike,Ofo bikes themselves are offline: their locations are tracked through users' cell phones. Users find a free bike, enter the license plate number into their app, and receive the bike unlock code. When they have reached their destination, they end the ride on the app and manually lock the bike. Rides cost 1 yuan for an hour and the deposit is 99 yuan.