题干

下列关于质点的说法,正确的是

A:质量很小的物体就可以当作质点

B:质量很大或体积很大的物体一定不能看成质点

C:体积很小的物体就可以看作质点

D:同一物体有时可看作质点,有时不能看作质点

上一题 下一题 0.0难度 选择题 更新时间:2016-04-13 08:43:42

答案(点此获取答案解析)

D

同类题2

根据短文内容,选择正确答案。

    Today, an increasing number of people are always looking at their mobile phones with their heads down. These people are called the "'Heads-down Tribe (低头族). Are you a heads-down tribe member? Heads-down tribe members now can be seen everywhere.

More and more traffic accidents are happening because more drivers use mobile phones when they are driving. In order to make drivers pay more attention to driving, some new traffic rules have been made. For example, people who use mobile phones while driving in Taiwan are fined (罚款). Car drivers and motorcyclists who break the traffic rule will be fined NT$ 3, 000 and NT$1, 000 respectively (分别地).

As we can see above, using mobile phones may cause accidents and even cost a lot of money. Also, more and more interesting and strange facts happen to the "Heads-down Tribe". Let's have a look at an interesting TV report. A man in America kept using his mobile phone on his way home. As a result, he knocked into a big lost bear. When he lifted his eves from the phone, he was so afraid that he turned around and ran away quickly. Another fact is that we can often see people in the restaurant eating face to face but looking at their own mobile phones. It's strange that they don't talk to the ones who sit opposite to them during the meal. Some of them even have fun communicating with others on the phone.

    Mobile phones are helpful and necessary tools for modern life. Are mobile phones good or bad? It depends on how people use them. Let's be "'healthy" users and try to be the "Heads--up Tribe".