问题 填空题

弹簧测力计下吊一个金属球,弹簧测力计的示数是10N,若将金属球缓慢进入水中,此时示数将逐渐______,金属球受到的浮力将逐渐______,若将金属球的一半浸入水中,弹簧测力计的示数是9N,这时金属球受到的浮力是______N,若完全浸没,示数将变为______N.

答案

(1)若将金属球缓慢进入水中,则金属球排开的水的体积逐渐变大,根据阿基米德原理可知:金属球受到的浮力将逐渐变大,而测力计示数为G-F,所以示数逐渐减小.

(2)当金属球刚好一半浸入水中时,金属球受到的浮力:

F=G-F′=10N-9N=1N;

当金属球全部浸入水中时,受到的浮力:

F′=2F=2×1N=2N,

此时弹簧测力计的示数:

F=G-F′=10N-2N=8N.

故答案为:减小;变大;1;8.

单项选择题
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".

Which of the following is TRUE according to(根据) this passage()

A.In Bulgaria, nodding heads means "no".

B.Jan taught English on a Pacific island.

C.Lisa was trying to buy some cabbage.

D.In India, only shaking heads means "yes".