如图所示，下列四个有关物体运动状态描述的图象中，不能说明物体_爱下问搜题

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问题选择题

如图所示，下列四个有关物体运动状态描述的图象中，不能说明物体处于平衡状态的是（　　）

A．

B．

C．

D．

答案

答案：D

题目分析：静止状态和匀速直线运动状态都是平衡状态．

根据图象判断出物体的运动状态即可解决此题．

A、路程不随时间变化，表示物体静止，处于平衡状态．故A不合题意．

B、路程与时间成正比，即速度不变，物体做匀速直线运动，处于平衡状态．故B不合题意．

C、速度不变，物体做匀速直线运动，物体处于平衡状态．故C不合题意．

D、物体做匀加速直线运动，不平衡．故D符合题意．

点评：本题关键要抓住平衡状态的特点：速度保持不变，而且可能是静止或匀速直线运动两种状态，不能漏解．

解答题

苹果每2千克3元，香蕉每3千克15元。李阿姨买8千克苹果和9千克香蕉，需要多少钱？

单项选择题

Editorial:
Critics of nuclear power complain about the allegedly serious harm that might result from continued operation of existing nuclear power plants. But such concerns do not justify closing these plants; after all, their operation has caused no more harm than that caused by pollution generated by coal and oilburning power plants, the most important other sources of energy.
Which of the following is an assumption on which the argument depends

A．Existing nuclear power plants should be closed only if it can be conclusively demonstrated that their continued operation is likely to cause harm more serious than the harm their operation has already caused.

B．Closing existing nuclear power plants would require greatly increased reliance on coal and oil-burning power plants.

C．The harm that has resulted from operation of existing coal and oil-burning power plants has been significant.

D．The harm that a nuclear power plant is likely to cause as it continues to operate can be reliably predicted from the past history of nuclear power plants.

E．(E) The only harm that has resulted from operation of existing coal and oil-burning power plants has resulted from the pollution generated by these plants.