“加速度计”作为测定物体加速度的仪器,已被广泛应用,如图所示为应变式加速度计的原

题型:计算题

问题:

“加速度计”作为测定物体加速度的仪器,已被广泛应用,如图所示为应变式加速度计的原理图。支架AB固定在待测系统上,滑块穿在AB之间的水平光滑杆上,并用轻弹簧连接在A端,其下端有一活动臂可在滑动变阻器上自由滑动,随着系统沿水平方向做变速运动,滑块相对于支架将发生位移,并通过电路转化为电信号从电压表输出,已知电压表量程为8V,滑块质量为m=0.1 kg,弹簧劲度系数k=20 N/m,电源电动势E=10 V,内阻不计,滑动 阻器总电阻R=40Ω,有效总长度l=8 cm,当待测系统静止时,滑动触头P位于变阻器R的中点,取A→B方向为速度正方向。

(1)确定该加速度计测量加速度的范围。

(2)为保证电压表能正常使用,则电路中R0至少应为多大?

(3)根据R0的最小值,写出待测系统沿A→B做变速运动时,电压表的输出电压Ux与加速度a的关系式。

(4)根据R0的最小值,将电压表上的表盘改成适当的加速度刻度,将对应的加速度值填入图中的小圆内。

考点:传感器的应用
题型:计算题

下图所示是举世闻名的中国皇家园林圆明园遗迹,该园林在1860年遭到西方列强的野蛮洗劫与焚毁。与此相关的列强侵华战争是

[ ]

A.鸦片战争

B.第二次鸦片战争

C.甲午中日战争

D.八国联军侵华战争

题型:计算题

患儿,男,2岁。因身材矮小就诊,10个月会坐,近1岁10个月会走,平时少哭多睡,食欲差,常便秘。体检:头大,前囟未闭,乳齿2个,反应较迟钝,喜伸舌,皮肤较粗糙,有脐疝。心肺无特殊发现。对该病例,首先应做的检查是()

A.血钙、血磷测定

B.T3、T4、TSH测定

C.智商测定

D.染色体检查

E.头颅CT检查

题型:计算题

下列不属于电磁波的应用的是[ ]

A.飞机上的飞行员和指挥部对话

B.微波炉加热食品

C.蓝牙技术(短距离无线电通信技术)

D.用B超检查身体

题型:计算题

()是PLC控制系统的中枢。

A.电源模板

B.中央处理单元CPU

C.输入输出接口模板

D.存储器

题型:计算题

The idea of test-tube babies may make you either delighted at the wonders of modern medicine or irritated while considering the moral, or legal, or technological implications of starting life in a laboratory. But if you’’ve ever been pregnant yourself, one thing is certain: You wonder what it’’s like to carry a test-tube baby. Are these pregnancies normal Are the babies normal The earliest answers come from Australia, where a group of medical experts at the Queen Victoria Medical Center in Melbourne have taken a look at the continent’’s first nine successful invitro pregnancies. The Australians report that the pregnancies themselves seemed to have proceeded according to plan, but at birth some unusual trends did show up. Seven of the nine babies turned out to be girls. Six of the nine were delivered by Caesarean section. And one baby, a twin, was born with a serious heart defect and a few days later developed life-threatening problems.What does it all mean Even the doctors don’’t know for sure, because the numbers are so small. The proportion of girls to boys is high, but until there are many more test-tube babies no one will know whether that’’s something that just happened to be like that or something special that happens when egg meets sperm in a test tube instead of a fallopian tube. The same thing is true of the single heart defect. It usually shows up in only 15 out of 60,000 births in that part of Australia, but the fact that it occurred in one out of nine test-tube babies does not necessarily mean that they are at special risk. One thing the doctors can explain is the high number of Caesareans. Most of the mothers were older, had long histories of fertility problems and in some cases had had surgery on the fallopian tubes, all of which made them likely candidates for Caesareans anyway.The Australian researchers report that they are quite encouraged. All the babies are now making normal progress, even the twin with the birth defects.

Which of the following statements about the experiment mentioned in the passage is true

A.Only the twins are defected.

B.Most of the babies are delivered by means of Caesarean.

C.There are some troubles during all mothers’ pregnancies.

D.One baby appears to be abnormal.

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