题干

如图所示,A、B两小球从O点水平抛出,A球恰能越过竖直挡板P落在水平面上的Q点,B球抛出后与水平面发生碰撞,弹起后恰能越过挡板P也落在Q点.B球与水平面碰撞前后瞬间水平方向速度不变,竖直方向速度大小不变、方向相反,不计空气阻力.则(   )

A:A、B球从O点运动到Q点的时间相等

B:A、B球经过挡板P顶端时竖直方向的速度大小相等

C:A球抛出时的速度是B球抛出时速度的3倍

D:减小B球抛出时的速度,它也可能越过挡板P

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B,C,D

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    Amazon is breaking into physical retail in a new way. The online retail giant revealed a new kind of physical store concept in a video published on Monday.

    The store, called Amazon Go, doesn't work like a typical Walmart or supermarket. Instead, it's designed so that shoppers will use an app, also called Amazon Go, to automatically add the products that they plan to buy to a digital shopping cart by scanning a QR code(二维码). They can then walk out of the building without waiting in a checkout line because Amazon will charge their Amazon account and send them a receipt.

    The first Amazon Go store is located in Seattle, where Amazon is headquartered. For years, there have been rumors the e-commerce company would expand its dominance from digital to physical shopping. Amazon began experimenting with physical bookstores a year ago, but Amazon Go may mark its boldest bet on physical ones yet. By removing much of the staff needed to operate a store, Amazon keeps costs lower than traditional competitors. It's also in a strong position to bring together data on its customers' shopping habits online and offline to make better suggestions in all situations.

    However, Amazon's move deeper into physical retail shops comes in a sensitive political climate. The company could be perceived as being a threat to some of the 3.4 million Americans who work as cashiers, according to the Bureau of Labor Statistics. On the campaign trail, Donald Trump repeatedly criticized Amazon and its founder Jeff Bezos for “getting away with murder tax-wise” and having “a huge antitrust(反垄断) problem.” Will the President& shy; elect add “job killer” to the list of criticisms?

    Amazon's effort to launch a new kind of retail store predates(在……之前) the rise of Donald Trump. “Four years ago we asked ourselves: what if we could create a shopping experience with no lines and no checkout? Could we push the boundaries of computer vision and machine learning to create a store where customers could simply take what they want and go?” The company says on an informational page about Amazon Go. For now, Amazon is starting slow. The Amazon Go is only open to Amazon employees in our Beta program, and is scheduled to open to the public in early 2017.

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