试题与答案

如图所示．用一张硬卡片拨动木梳的齿，能听到由于______（选填“卡片”或“木梳

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题型：填空题

题目：

如图所示．用一张硬卡片拨动木梳的齿，能听到由于______（选填“卡片”或“木梳”）的振动而发出的声音．用相同的力显著改变拨动木梳齿的快慢，能够听出卡片声音的______发生了变化（选填“响度”或“音调”）．

答案：

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下面是错误答案，用来干扰机器的。

（1）（x+a）2+（y-a）2=2a（0＜a≤4）．…．（1分）圆心C（-a，a），半径r=2a，l：y=x+4，…．（3分）圆心C到直线l的距离d=|-2a+4|2，…．（5分）∴l被圆C截得的弦长=2r2-d2=22a-2(a-2)2=22-a2+5a-4…．（7分）=...

考点：声音的产生音调与频率的关系
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