(10分)质量为10 kg的物体在拉力作用下运动, 求下列四种情况拉力做的功:

题型:计算题

问题:

(10分)质量为10 kg的物体在拉力作用下运动, 求下列四种情况拉力做的功: ( sin370=0.6,cos370="0.8," g=10m/s2)

⑴拉力沿水平方向, 物体在动摩擦因数为0.25的水平地面上匀速移动4 m.

⑵拉力沿水平方向, 物体在动摩擦因数为0.25的水平地面上以2 m / s2的加速度匀加速移动4 m.

⑶用大小为50N,沿水平方向的拉力拉物体在光滑的水平地面上移动4 m.

⑷用大小为50N,方向与水平面成37°角的斜向上的拉力拉物体, 使物体沿水平地面移动4m, 物体与地面间的动摩擦因数为0.25.

考点:
题型:计算题

下列实验操作正确的是(  )

A.

点燃酒精灯

B.

100mL量筒量取9mL的液体

C.

称量固体质量

D.

不断搅拌

题型:计算题

进度的实际值指的是对应于里程碑事件或再细化的分项工作的( )。

A.分解进度

B.实际进度

C.进度计划

D.进度目标值

题型:计算题

Kids are far better than adults at learning how to speak multiple languages. Research now shows that very young infants might have some of the best language skills of all.

A new study suggests that babies between 4 and 6 months old can tell the difference between two languages just by looking at the speaker's face.They don't need to hear word.Sometimes between 6-8 months of age, babies raised in homes where just one language is spoken lose this ability.Babies from bilingual(双语的) homes, on the other hand, keep the face-reading ability until they're at least 8 months old.

Researchers in Canada studied 36 babies from English-speaking families.Twelve of the babies were 4 months old,12 were 6 months old, and the rest were 8 months old.Each baby sat on his or her mother's lap and watched video clips(电影片断) of a woman talking.The woman was fluent in both English and French.In some clips, she read from a storybook in English.In other clips, she read in French.In all of the videos there was no sound.

小题1:What is mainly discussed in the passage ?

A.Language teaching.

B.Language learning

C.Babies and language learning

D.Parents and language teaching小题2:What do the underlined word in the second paragraph refer to ?

A.Two or more.

B.Foreign.

C.difficult.

D.At least one.小题3:We can know from the passage that    .

A.all the babies in the study are of the same age.

B.the babies could hear the woman's voice while watching the videos.

C.the stories the woman read were written in either French or German.

D.it's still unknown how babies could tell the difference between languages.小题4:Why did the 8-month-old pay no attention when the language was changed ?

A.They had lost the ability to distinguish different languages.

B.They were too tired to open their eyes and fell asleep.

C.They couldn't hear what the speaker was talking about.

D.They had lost the interest in bilingual speakers.

题型:计算题

下列句子没有意动用法的一句是  [ ]

A.越国以鄙远,君知其难也

B.阙秦以利晋,唯君图之

C.顷之未发,太子迟之

D.秦武阳色变振恐,群臣怪之

题型:计算题

血沉测定(魏氏法)影响因素有哪些?

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