问题 计算题

(12分)如图所示,AB为竖直半圆轨道的竖直直径,轨道半径R=0.9m,轨道B端与水平面相切,质量m=1kg的光滑小球从水平面以初速度V0向B滑动,取g=10m/s2

(1)若V0=6m/s,求小球经轨道最低点B瞬间对轨道的压力为多少?

(2)若小球刚好能经过A点,则小球在A点的速度至少为多大?小球离开A点后在水平面的落点与B点的距离为多少?

答案

见题目分析

题目分析:

(1)小球在B点的受力分析如图:

由牛顿第二定律有:              (公式2分)

解得小球受到的支持力N==50N        (答案1分)

由牛顿第三定律可知,小球对道轨的压与与N大小相等,方向相反。   (1分)

(2)小球恰好过最高点,即只由重力提供向心力有:

                                     (2分)

解得小球在A点的最小速度:    (1分)

小球离开A点后做平抛运动有:        (2分)

                                        (2分)

解得t=0.6s    s=1.8m                          (1分)

选择题
阅读理解

Ad. 1

April fool’s party

On Friday, April 1, Inner Affair goes back to the days of funk! Classic Tunes from the 70’s and 80’s by DJs Den & Sion. 9pm till late.

Tickets: Free entrance for those in costume, otherwise 50 yuan (US$6)

Time/date: 9 pm, April 1

Place: Inner Affair, 1/F Qiankun Dasha, 6 Sanlitun Xiliujie, Chaoyang District

Tel: 8454 0321

Ad. 2

Language in use

Enjoy free inhouse coffee, tea and beer as well as music and dancing. Practice your Chinese, make friends and have fun.

Time/date: 7 to 9 pm, March 25

Place: Language In Use Club, 2/F, Science Fortune Center, 8 Xueqing Lu, north of Xueyuan Lu, Haidian District

Ad. 3

The "worst" party

Organized by ozone productions, the party is set to be "the worst ever", with the lamest music from the 60s, 70s and 80s. Special prizes will be awarded to the worst dressed or for bad fashion sense.

Tickets: Free entrance

Time/date: 9 pm, April 1

Place: Pula Pula, Tianze Lu, Oriental Seven Colours Plaza, Chaoyang District

Tel: 64668575

Ad. 4

La Nuit Francaise

Again on the 2nd Thursday of the month La Nuit Francaise will be held at Le Rendezvous. The monthly event is an opportunity for all French people and everyone interested in France or speaking French to gather together.

The evening features three glasses of wine and canapes for participants and a special exhibition.

Time/date: 7 to 10 pm, April 14

Place: Le Rendezvous, 3 Gongti Beilu, accross from the Pacific Century Plaza, Chaoyang District Tel: 64629110

Ad. 5

Marco V

Dutch DJ Marco V drops by Banana for a gig which is supported by Hong Kong’s DJ Spark.

Marco V has been around for many years, as an inventive, styleblending deejay and a successful and devoted producer. His spinning is energetic, crowdpleasing and never sees an empty dance floor. He was ranked No. 15 in this year’s international DJ MAG DJ Top100.

Tickets: 40 yuan (US$4.80) in advance, 50 yuan (US$6) at the door, both include a free drink

Time/date: 10 pm to 4 am, March 31, April 1

Place: Banana, in the lobby of the Scitech Hotel, 22 Jianwai Dajie, Chaoyang District

Tel: 65283636

小题1: Which of the following is NOT true of Ad. 1 and Ad. 3?

A.The two parties will be held on the same day.

B.The two parties will be held at the same time.

C.The entrance fees of the two parties will not be charged.

D.Some old music will be played at the parties.小题2:Which of the following is intended for the Chinese learners?

A.Marco V.

B.La Nuit Francaise.

C.Language in use.

D.The "worst" party.小题3:We can infer that______.

A.Marco V is a newlyestablished band

B.La Nuit Francaise may be French words

C.the "worst" party will attract a lot of college students

D.you will enjoy free drink at April fool’s party