问题 选择题

下列说法正确的是

A.合外力对质点做的功为零,则质点的动能、动量都不变

B.合外力对质点施的冲量不为零,则质点动量必将改变,动能也一定变

C.某质点受到合力不为零,其动量、动能都改变

D.某质点的动量、动能都改变,它所受到的合外力一定不为零

答案

答案:D

合外力对质点做功为零,则物体速度大小不变,则质点的动能不变,如果速度方向改变,则动量变化。合外力对质点施加的冲量不为零,则质点动量必将改变,如果仅速度方向改变但速度大小不变,则动能不变。某质点受到合力不为零,可能只有方向或大小改变,则其动量、动能只有一个改变。答案选D。

单项选择题 B型题
阅读理解

My name is Chelsea Chowderhead. A chowder is a kind of soup. I was laughed at because of my last name as soon as I started school. So when my family moved to South Carolina, I asked my dad if I could change my name.

“You shouldn’t change who you are. Let people get to know you first and your name later. When you meet someone new, ask them a good question, something you’re really interested in. Once people start talking about themselves, they don’t judge(评价) you.”

Two days later I headed to my new school for the first day of class. At lunch, I noticed that there were twin brothers who were talking to each other. I remembered my dad’s advice, so I decided to try.

I noticed that their lunchboxes were identical. “What’s it like being a twin?” I asked.

They looked surprised. Then one said, “No one has ever asked us that!”

“Most of the time it’s good,” the other said. “When you’re a twin you always have someone to talk to and have lunch with.”

In no time we were laughing and talking. Then one of the brothers said, “I’m Nicholas, and this is my brother, Nathaniel. What’s your name?”

I took a deep breath and said, “I’m Chelsea Chowderhead.”

“Chowder? Like the soup?” asked Nathaniel.

“Yes,” I replied, looking down.

“Hey, cool! Do you want to come over after school and play basketball with us?” Nathaniel asked. I nodded.

And that is how I became friends with the twin brothers.

小题1:Why did the writer want to change his name?

A.People made fun of it.

B.He wanted to make more friends.

C.It was hard to remember.

D.He wanted to be cool in the new school.小题2:The writer’s father advised him to ____________.

A.move to a new class

B.say hello to others

C.share his interests

D.ask good questions小题3:The underlined word “identical” in Paragraph 4 probably means _____________.

A.same

B.beautiful

C.big

D.full小题4:When the twin brothers asked his name, the writer felt ________________.

A.surprised

B.angry

C.nervous

D.proud小题5:Which of the following is TRUE according to the passage?

A.One can order a chowder in some restaurants.

B.The twins said hello to the writer first.

C.The twins also didn’t like the writer’s name.

D.At last the writer changed his name.