搜题请搜索小程序“爱下问搜题”
问题 计算题

（2012年2月山东潍坊重点中学联考）一列横波在x轴上传播，在tl=0时刻波形如图中实线所示，t2=0.05s时刻波形如图中虚线所示,且此时x=6m处的质点正从平衡位置向下振动.

①这列波的振幅和波长；

②已知，波速大小及方向.

答案

见解析

①振幅A=0．2m； ① 波长λ=8 m  ②

②波沿x轴负方向传播 ③

由于，故④

由波速公式v=λ/T得v=280m/s。⑤

判断题

计算机病毒只要人们不去执行它，就无法发挥其破坏作用。( )
查看答案
填空题

In the last 500 years, nothing about people—not their clothes, ideas, or languages— has changed as much as what they eat. The original chocolate drink was (26) the seeds of the cocoa tree by South American Indians. The Spanish (27) it to the rest of the world during the 1500s. And although it was very expensive, it quickly became (28) In London shops where chocolate drinks were served became important meeting places. Some still exist today.
The potato is also from the New World. (29) 1600, the Spanish brought it from Peru to Europe, where it soon was widely grown. Ireland became so (30) on it that thousands of Irish people starved when the crop failed during the "Potato Famine" of 1845 to 1846, and thousands more were forced to emigrate to America.
There are many other foods that have (31) from South America to the Old World. But some others went in the opposite direction. Brazil is now the World’s largest grower of coffee, and coffee is an important crop in Colombia and other South American countries. But it is (32) to Ethiopia. It was first made into a drink by Arabs during the 1400s.
According to an Arabic legend, coffee was (33) when a goatherd noticed that his goats were attracted to the red berries on a coffee bush. He tried one and (34) the "wide-awake" feeling that one third of the world’s population now (35) the day with.

In the last 500 years, nothing about people—not their clothes, ideas, or languages— has changed as much as what they eat. The original chocolate drink was (26) the seeds of the cocoa tree by South American Indians. The Spanish (27) it to the rest of the world during the 1500s. And although it was very expensive, it quickly became (28) In London shops where chocolate drinks were served became important meeting places. Some still exist today.
The potato is also from the New World. (29) 1600, the Spanish brought it from Peru to Europe, where it soon was widely grown. Ireland became so (30) on it that thousands of Irish people starved when the crop failed during the "Potato Famine" of 1845 to 1846, and thousands more were forced to emigrate to America.
There are many other foods that have (31) from South America to the Old World. But some others went in the opposite direction. Brazil is now the World’s largest grower of coffee, and coffee is an important crop in Colombia and other South American countries. But it is (32) to Ethiopia. It was first made into a drink by Arabs during the 1400s.
According to an Arabic legend, coffee was (33) when a goatherd noticed that his goats were attracted to the red berries on a coffee bush. He tried one and (34) the "wide-awake" feeling that one third of the world’s population now (35) the day with.
查看答案