如图所示，是一列简谐横波在某时刻的波形图.若此时质元P正处于加_爱下问搜题

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问题选择题

如图所示，是一列简谐横波在某时刻的波形图.若此时质元P正处于加速运动过程中，则此时( )

A．质元Q和质元N均处于加速运动过程中

B．质元Q和质元N均处于减速运动过程中

C．质元Q处于加速运动过程中，质元N处于减速运动过程中

D．质元Q处于减速运动过程中，质元N处于加速运动过程中

答案

答案：D

题目分析：因为质元P处于加速过程，所以质元P向平衡位置运动，由此可知波沿x轴负方向运动，所以质元Q沿y轴正方向运动，远离平衡位置，速度减小，质元N沿y轴正方向运动，靠 * * 衡位置，速度增大，故选项ABC错误D正确．

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单项选择题

In Swartkans territory, archaeologists discovered charred bone fragments dating back 1 million years. Analysis of the fragments, which came from a variety of animals, showed that they had been heated to temperatures no higher than those produced in experimental campfires made from branches of white stinkwood, the most common tree around Swartkans.
Which of the following, if true, would, together with the information above, provide the best basis for the claim that the charred bone fragments are evidence of the use of fire by early hominids

A．The white stinkwood tree is used for building material by the present-day inhabitants of Swartkans.

B．Forest fires can heat wood to a range of temperatures that occur in campfires.

C．The bone fragments were fitted together by the archaeologists to form the complete skeletons of several animals.

D．Apart from the Swartkans discovery, there is reliable evidence that early hominids used fire as many as 500 thousand years ago.

E．(E) The bone fragments were found in several distinct layers of limestone that contained primitive cutting tools known to have been used by early hominids.