题干

用大小不变的水平力,拉木块沿水平桌面上做匀速直线运动。木块在运动过程中,下列说法正确的是(    )

A:木块对桌面的压力和木块受到的重力是一对平衡力

B:木块受到的滑动摩擦力大小保持不变

C:绳对木块的拉力大于桌面对木块的摩擦力

D:绳对木块的拉力和木块对绳的拉力是一对平衡力

上一题 下一题 0.0难度 选择题 更新时间:2017-11-21 03:56:20

答案(点此获取答案解析)

B

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任务型阅读

    Every time we get behind the wheel of a car, we put our lives and the lives of others at risk. Self-driving cars are designed to reduce those risks by letting technology control our vehicles.

    Accident rates for self-driving cars have been much lower than the rate, for human-driven cars. ____

    As humans, we can make moral choices in avoiding accidents. To avoid hitting a child, for example, human drivers might sharply turn a car away from the child even if others may be injured. ____ Researchers studied this issue. They have developed the Moral Machine website to help explore the choices self-driving cars should make.

    ____ You are shown two possible traffic situations and you choose between them. An accident will take place. You choose how many living beings would be hurt or killed.

    In one situation there may be a female doctor, a child, two dogs and a homeless person who would be killed. In the other situation, you might have two babies and a cat who would be killed. ____

    The Moral Machine website has many situations and many possible outcomes. When you click on the situation of your choice, it will be highlighted. ____ At the end of the situation, you are shown the results, based on the choices you made. The results show which character you were most likely to save and which character you were most likely to have die.

A. Who should those victims be?

B. Then the next situation appears.

C. You choose who lives and who dies.

D. You can use the Moral Machine to be the judge.

E. But what moral choices can self-driving cars make?

F. The Moral Machine website lets you choose how you would react in a collision.

G. Google's self-driving car has had only 13 collisions after traveling 1.8 million miles.