题干

放在水平桌面上的木块处于静止状态,下列各对力中是平衡力的是 (       )

 

A:木块的重力和木块对桌面的压力

B:木块对桌面的压力和桌面对木块的支持力

C:木块的重力和桌面对木块的支持力

D:木块的重力和木块对桌面的吸引力

上一题 下一题 0.0难度 选择题 更新时间:2019-12-23 06:51:27

答案(点此获取答案解析)

C

同类题3

阅读下面短文,在空白处填入一个适当的词,或填入括号中所给单词的正确形式(每空不多于3个单词)。

    Long ago there lived a kind old man. One day while walking through the woods, the old man found a butterfly's cocoon(茧). He took ____ home. A few days later, a small opening appeared. He sat and watched the butterfly ____ several hours as it struggled(挣扎) to force its body through that little hole.

    Then the nice man decided ____ (help) the butterfly, so he cut the remaining bit of the cocoon. The butterfly then came out ____ (easy). But it had a fat body and small, shriveled(皱缩的) wings. The man continued to watch the butterfly because he expected that, at any moment, the wings would enlarge and expand to be able to support the body ____ would grow small in time. However, neither happened. In fact, the butterfly spent the rest of its life ____ (lie) with a fat body and shriveled wings. It was never able to fly.

    What the man did not understand was that the struggle was a must for the butterfly to get through the tiny opening. That's the ____ (nature) way of forcing fluid(营养液) from the body of the butterfly into its wings.

    In this way, it would be ready for flight when it achieved its freedom from the cocoon. Sometimes struggles are exactly ____ we need in our life. If we ____ (allow) to go through our life without any ____ (difficult), it will weaken us. We won't be strong as what we could have been. And we can never fly.

同类题5

任务型阅读

    Arguments happen in every healthy relationship—we know it sounds contradictory, but it's true—but they can still have a negative impact if they aren't handled properly. ____

    Take a breath. We know that it can be hard to think clearly when you are angry, so we would first like to encourage you to try to take a second to collect your thoughts before engaging in a dialogue with your partner. ____ If you are not careful you could potentially say what might damage your relationship.

    Take the situation as it is. Even though you are angry and it can be hard to be objective, try to see the situation for what it is. Do not escalate (不断恶化) the argument. ____Try to understand the purpose behind the action—if something happened accidentally, you should not treat as if it were done intentionally.

    ____ If you have done something wrong, the best possible option for you is to admit it. Denying something only makes it more hurtful and often your partner will be able to forgive you much more quickly if you are honest.

    Set ground rules. After a fight you and your partner can have a heart-to-heart talk of what happened. ____ At this point you can set some ground rules for future fights, like not cursing each other or calling each other's names, which might help reduce the intensity of your fights.

    Fighting with someone is never easy. And it's especially difficult when you are arguing with someone that you care about. Thinking carefully and controlling yourself during an argument can help you avoid saying something that could permanently hurt your relationship.

A. Take positive action.

B. Avoid making excuses.

C. Anger can be poisonous.

D. Here is how to maintain good relationship.

E. You can discuss what hurts each of you and how you can move forward.

F. The trick to prevent an argument from destroying your relationship is learning how to fight fair.

G. Ask yourself if this situation is worth arguing about.