题干

为了探究滑动摩擦力,小超同学利用牙刷做实验,当用力匀速拖动牙刷时,刷毛发生了如图所示的弯曲,对这个实验的分析正确的是(    )

A:刷毛弯曲越厉害说明牙刷受到的力越小

B:手的拉力和牙刷受到的摩擦力不平衡

C:牙刷受到的摩擦力作用在刷毛上

D:从刷毛弯曲的方向可以判断牙刷受到摩擦力的方向向右

上一题 下一题 0.0难度 选择题 更新时间:2017-05-31 10:43:16

答案(点此获取答案解析)

C

同类题1

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项,选项中有两项为多余选项。

How to Prepare for Guests

    Guests are people whom we welcome sincerely and we should make sure they feel comfortable like they are in their home. Sometimes we get enough time to make preparations for guests, but sometimes we don't. This article will be beneficial for both these kinds of people. ____

    Get a bedroom for your guests. It doesn't have to be complicated. Change bed covers, clean the bathroom and you can even add a nice scented(芬芳的) candle to spice things up. These are simple things you can do even if you are a very busy person. ____

    Know what your guests' favorite foods are so that you can make for them and serve. Don't forget to note down if they are allergic to any certain kind of food to save the embarrassment(难堪). If you are among one of those people who can hardly manage the time to cook for your guests then take them to the restaurants so that they can taste new foods or enjoy their favorite ones.

    Plan activities to have a good time with your guests. ____ If they come over the weekends then plan for some indoor activities to have fun. It's also a good way to remove your tiredness from your boring life.

    ____ It can happen that you may not be able to be with your guests for a certain amount of time while they are staying in your home. In that case you must declare it to them and may have someone else to accompany them while you are absent.

    When your guests say goodbye, give them something as a token(信物) of love to remember the days they stayed with you. ____

A. Declare your absence.

B. Allow them to come and go as they please.

C. Just bear in mind everything fresh and clean will do fine.

D. If they come during the vacation then you can plan for outdoor activities.

E. Here are some ways to help you to put away things well in a short amount of time.

F. Make your guests feel even more welcome by including them in activities such as outings, or movies.

G. It can be just a photo in a beautiful frame that will remind them of beautiful moments that they spent with you.