如图所示利用动滑轮提升货物,动滑轮重为20牛顿,绳与动滑轮间的摩擦及绳子重不计.

题型:选择题

问题:

如图所示利用动滑轮提升货物,动滑轮重为20牛顿,绳与动滑轮间的摩擦及绳子重不计.第一次把重为100牛顿的货物匀速提升,这个过程动滑轮的机械效率为η1;第二次把重为200牛顿的货物匀速提升,这个过程动滑轮的机械效率为η2.则

[ ]

A.η1<η2

B.η1>η2

C.η12

D.η1和η2的关系无法确定

考点:滑轮(组)的机械效率
题型:选择题

Mr. Gao lives in a town. When he was twenty-five, his son was born. He calls him Gao Ling. The little boy is clever. He and his wife love him very much. It’s September 1st today. A new school year begins. Gao Ling is happy and wears his most beautiful clothes. He’s going to school with his new bag. “Let me take you to school, dear.” said Mrs. Gao. “Thank you, Mummy,” said the boy. “The school is not far from here. I can go there myself.”

  At school a teacher met the little boy and asked, “What’s your name, my little friend?” “Gao Ling, sir.” answered the boy. “How old are you?” “Six, sir.” “What’s your father’s name?” “Gao Daling, sir.” “How old is he?” “He is six, too, sir.” “Oh,” the teacher said in surprise. “Is he as old as you?”

  “Yes, sir,” said the boy. “He became a father only on the day when I was born.”

根据短文内容,选择正确答案(10分)

小题1:Mr. Gao is _____now.

A、six                 B、twenty-five          C、thirty one

小题2:Mr. and Mrs. Gao love their son because_____.

A、the boy is clever

B、he likes to go to school

C、he can go to school himself

小题3:Gao Ling didn’t let his mother take him to school because_____.

A.she was too busy

B.his friends could took him

C.the policeman could help him

D.the school is near and he could take care of himself小题4:Gao Ling went to school_____.

A、by car                  B、on foot              C、by train

小题5:Gao Ling thought_____.

A、his father and he were born on the same day

B、his father was younger than him

C、Gao Daling became a father only for six years

题型:选择题
Sina said she _________to school the next Saturday.

A. didn't go
B. isn't go
C. wouldn't go
D. won't go
题型:选择题

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在新股定价发行方式下,每一账户申购股票数量不设上限。( )

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