问题 选择题

如图所示,升降机天花板上用轻弹簧悬挂一物体,升降机静止时弹簧伸长量为10cm,运动时弹簧伸长量为9cm,则升降机的运动状态可能是(g=10m/s2)(  )

A.以a=1m/s2的加速度加速上升

B.以a=1m/s2的加速度加速下降

C.以a=9m/s2的加速度减速上升

D.以a=9m/s2的加速度减速下降

答案

设物体的质量为m,弹簧的劲度系数为k.

静止时,mg=kx1

当弹簧伸长减小时,弹力减小,小球所受合力方向竖直向下,小球的加速度竖直向下.

根据牛顿第二定律得:mg-kx2=ma,x2=

9
10
x1

代入解得 a=1m/s2,方向竖直向下,则升降机可能以1m/s2的加速度减速上升,也可能以1m/s2的加速度加速下降.

故选B.

阅读理解

Here are two amazing shops from the world.

One of the most famous department stores in New York City is Macy's.There are over 850 Macy's stores all over the US, but the flagship store is in Herald Square,Manhattan---just around the corner from the Empire State Building. Interestingly, Rowland Macy, the company founder ( 创始人 ), opened his first shops between 1843 and 1855, but they weren't   successful. However, Macy learned from his mistakes, and in 1858 he moved to New York. He opened his first New York store on October 18, 1858 and was immediately successful. Macy's is especially famous for its Thanksgiving Day Parade, which marks the beginning of the Christmas season.

One of the oldest shops in London is Fortnum & Mason.

It was founded by William Fortnum and Hugh Mason in

1707 in central London. Originally, the shop only sold food, but these days, it sells all kinds of other things including clothes, books and games. It has the "Gentleman's  Department" on the top floor, a famous tea shop and several restaurants. The business started out small, but in 1761, William Fortnum’s grandson, Charles, went to work for Queen Charlotte. As a result, the royals ( 皇家 )  started shopping there and continues to now. In fact, Queen Elizabeth visited Fortnum's last year. Fortnum's is really famous for its hampers, which are baskets of food. There are picnic hampers and Christmas hampers that are full of wines and Christmas food. They are extremely popular, but also expensive and can cost up to £25.000.

根据材料内容选择最佳答案,并将其标号涂在答题卡相应位置。

小题1: How old is the store Macy's which was first opened in New York?

A.60.

B.158.

C.155.

D.160.小题2: What made Rowland Macy's shops successful?

A.He moved to New York.

B.He opened a flagship store.

C.He began Christmas season.

D.He learned from his mistakes.小题3:What did Fortnum & Mason use to sell?

A.Food.

B.Books.

C.Games.

D.Clothes.小题4:. Which of the following is NOT true?

A.Fortnum & Mason used to be a small shop.

B.The hampers from Fortnum & Mason are popular but expensive.

C.Macy's Thanksgiving Day Parade means the beginning of Christmas season.

D.William Fortnum worked for Queen Elizabeth.小题5:Where is this passage possibly from?

A.A music magazine.

B.A clothes ad.

C.A sports poster.

D.A fashion guidebook.

多项选择题