问题 选择题

下列说法正确的是(  )

A.速率是指瞬时速度的大小

B.平均速度就是速度的平均值

C.火车以速度v经过某一段路,v是指瞬时速度

D.子弹以速度v从枪口射出,v是指平均速度

答案

A、速率是指瞬时速度的大小.故A正确.

    B、当物体做匀变速直线运动时,平均速度等于速度的平均值,而非匀变速直线运动,则不一定.故B错误.

    C、火车以速度v经过某一段路,v是指平均速度.故C错误.

    D、子弹以速度v从枪口射出,v是指瞬时速度.故D错误.

故选A

单项选择题
单项选择题

Vienna was one of the music centers of Europe during the classical period, and Haydn, Mozart, and Beethoven were all active there. As the (1) of the Holy Roman Empire (which included parts of present-day Austria, Germany, Italy, Hungary, Czech and Slovakia), it was a (2) cultural and commercial center (3) a cosmopolitan character. Its population of almost 250,000 (in 1800) made Vienna the fourth largest city in Europe. All three (4) masters were born elsewhere, but they were (5) to Vienna to study and to seek (6) . In Vienna, Haydn and Mozart became close friends and influenced each other’s musical (7) . Beethoven traveled to Vienna at sixteen to play for Mozart; at twenty-two, he returned to study with Haydn.

Aristocrats from all over the Empire spent the winter in Vienna, sometimes bringing their private (8) . Music was an important part of court life, and a good orchestra was a (9) of prestige. Many of the nobility were excellent musicians.

Much music was heard in (10) concerts where aristocrats and wealthy commoners played (11) professional musicians. Mozart and Beethoven often earned money by performing in these intimate concerts. The nobility (12) hired servants who could (13) as musicians. An advertisement in the Vienna Gazette of 1789 (14) : " Wanted, for a house of the gentry, a manservant who knows how to play the violin well. "

In Vienna there was also (15) music, light and popular in (16) . Small street bands of wind and string players played at garden parties or under the windows of people (17) to throw (18) money. Haydn and Mozart wrote many outdoor entertainment (19) , (20) they called divertimentos or serenades. Vienna’s great love of music and its enthusiastic demand for new works made it the chosen city of Haydn, Mozart and Beethoven.

11()

A.along

B.alongside

C.among

D.between