问题 选择题

如图所示,用10N的水平推力推着重为60N的物体沿水平方向做直线运动.若推力对物体做了60J的功,则在这一过程中(  )

A.物体一定受到10N的摩擦力

B.重力做的功一定为360J

C.物体一定运动了1m

D.物体一定运动了6m

答案

物体受到的力F=10N,做功的大小W=60J,

s=

W
F
=
60J
10N
=6m,即物体水平向右移动了6m.

由于物体不一定是做匀速直线运动,故推力与摩擦力不一定相等,故A错误,重力的方向是竖直向下的,没有做功,故B错误.

故选D.

单项选择题
阅读理解

阅读理解。

     We have two daughters: Kristen is seven years old and Kelly is four. Last Sunday evening, we invited

some people home for dinner. I dressed them nicely for the party, and told them that their job was to join

Mommy in answering the door when the bell rang. Mommy would introduce them to the guests, and then

they would take the guests'coats upstairs and put them on the bed in the second bedroom.

     The guests arrived. I introduced my two daughters to each of them. The adults were nice and kind and

said how lucky we were to have such good kids.

     Each of the guests made a particular fuss over Kelly, the younger one, admiring her dress, her hair and

her smile. They said she was a remarkable girl to be carrying coats upstairs at her age.

     I thought to myself that we adults usually make a big "to do" over the younger one because she's the one

who seems more easily hurt. We do it with the best of intentions.

     But we seldom think of how it might affect the other child. I was a little worried that Kristen would feel

she was being outshined. I was about to serve dinner when I realized that she had been missing for twenty

minutes. I ran upstairs and found her in the bedroom, crying.

     I said, "What are you doing, my dear?"

     She turned to me with a sad expression and said,"Mommy, why don't people like me the way they like

my sister? Is it because I'm not pretty? Is that why they don't say nice things about me as much?"

     I tried to explain to her, kissing and hugging her to make her feel better.

     Now, whenever I visit a friend's home, I make it a point to speak to the elder child first.

1. What did the parents ask the sisters to do to welcome the guests?

A. To introduce themselves to the guests

B. To put away the guests' coats in another upstairs room.

C. To take off the guests' coats politely.

D. To entertain the guests with candies.

2. The underlined expression' make a big "to do" over' (paragraph 4) means ______.

A. show much concern about

B. have a special effect on

C. list jobs to be done for

D. do good things for

3. The guests praised Kelly for carrying coats upstairs because of her ______.

A. beautiful hair

B. pretty clothes

C. lovely smile

D. young age

4. Kristen felt sad and cried because ______.

A. the guest gave her more coats to carry

B. she didn't look as pretty as Kelly

C. the guests praised her sister more than her

D. her mother didn't introduce her to the guests

5. We can conclude from the passage that ______.

A. parents should pay more attention to the elder children

B. the younger children are usually more easily hurt

C. people usually like the younger children more

D. adults should treat children equally