问题 选择题

如图所示,小车处在水平桌面上,用轻绳跨过定滑轮与钩码相连,在轻绳的拉力作用下沿桌面做匀速运动.若突然剪断轻绳,则小车(   )

A.将继续向前匀速运动

B.运动将越来越慢

C.将立即停止运动

D.受的摩擦力将不变

答案

BD

题目分析:A.剪断轻绳,小车失去拉力作用,由于惯性将将继续向前但减速,故A错误;

B.由于受到摩擦力,又失去拉力,所以运动将越来越慢,故B正确;

C.由于惯性不会立即停止运动,故C错误;

D.由于小车的重不变,压力不变,接触面的粗糙程度也不变,所以小车受的摩擦力将不变,故D正确。

故选BD。

点评:主要考查了惯性的知识,关键是D选项要明确影响摩擦力的因素都没有改变,所以摩擦力不变。

单项选择题

Living in a foreign culture can be exciting, but it can also be confusing. A group of Americans who taught English in other countries recently discussed their experiences. They decided that miscommunications were always possible, even over something as simple as "yes" and "no".

On her first day in Micronesia, an island in the Pacific, Lisa thought people weren’t paying any attention to her. The day was hot. She went into a store and asked, "Do you have cold drinks" The woman there didn’t say anything. Lisa repeated the question. Still the woman said nothing. She later learned that the woman had answered her: She had raised her eyebrows, which in Micronesia means "yes".

Jan remembered an experience she had in Bulgaria, a country in Europe. She went to a restaurant that was known for its cabbage. She asked the waiter, "Do you have cabbage today" He nodded his head. Jan waited, but the cabbage never came. In that country, a nod means no.

Tom had a similar problem when he arrived in India. After explaining something in class, he asked his students if they understood. They answered with many different nods and shakes of the head. He thought some people had not understood, so he explained again. When he asked again, they did the same thing. He soon found out that his students did understand. In India, people nod and shake their heads in different ways depending on where they come from. You have to know where a person is from to understand whether they mean "yes" or "no".

The passage is mainly about()

A.body language in foreign restaurants

B.class discussion in Indian schools

C.miscommunication in different cultures

D.English teaching in other countries

判断题