小红用一水平的力去推地面上的桌子，但未推动，这是因为（） _爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

小红用一水平的力去推地面上的桌子，但未推动，这是因为（　　）

A．推力小于此时桌子受到的摩擦力

B．桌子受到的重力与地面对桌子的支持力平衡，所以桌子水平方向不动

C．小红对桌子的推力等于桌子对小红的推力

D．推力与地面对桌子的摩擦力平衡，合力为零

答案

A、推桌子时桌子在水平向上受推力，但桌子没有动，说明摩擦力和推力平衡，而不是推力小于摩擦力，所以A错．

B、桌子受重力与支持力平衡，使桌子在竖直方向平衡，所以B错．

C、对桌子的推力与桌子推人的力是相等的，但这不是桌子平衡的原因．所以C错．

D、桌子不动，则桌子受力平衡，推力与地面对桌子的摩擦力平衡，合力为零，D正确．

故选D．

阅读理解

Reading comprehension.

ASK LASKAS
YOU'VE GOT QUESTIONS. SHE'S GOT ANSWERS

My children go to a primary school where they are not allowed to play football
in the playground for fear that a child might be hurt. Besides, now the school
says there must be no homework because the local secondary school can't

keep up with the amount of homework given in the primary school. Can the school do this?
Puzzled Dad

It can't if enough parents do something about it. It is not just schools. We live in
a society which wishes to get rid of risk. However, schools should have a little
common sense and courage. Children need risk if they arc to grow up self-sufficient

and confident. They need homework, too, if they are to fulfill their academic potential.
Complain, loudly.

I have a beautiful teenage daughter who spends an hour making up her face in
front of the mirror every day. I tell her to go easy. She just gets mad or bursts
into tears. How can I make her understand she's beautiful the way she is.
Plain Mom

You can't. Your daughter is at the age when she's trying to look beautiful, trying
on new masks. And if her friends all dress up as she docs, you're in for an extra
hard time. Support her and tell her she's beautiful-even if she looks ridiculous for
now. Then invite her to join you for a day at a spa (健康美容中心). Let her try

various looks until she's comfortable in her own skin.

1. Why are the children not allowed to play football in the playground?

A. The school is afraid that children might be injured.
B. The school is not sensible and confident.
C. The children don't have enough time to do homework.
D. The children may fail to fulfill their academic potential.

2. What disturbs Plain Mom is that her daughter ______.

A. becomes mad
B. cries a lot
C. spends much rime before the mirror
D. is not beautiful enough

3. The solution to Plain Mom's problem is to ______.

A. make her daughter look less ridiculous
B. let her daughter dress up like her friends
C. make her daughter go to a spa every week
D. let her daughter feel herself what beauty is

填空题

表示设备断开和允许进入间隔的信号及电压表的指示等，均不得作为设备（）的根据，应验电。如果指示有电，禁止在该设备上作业。