问题 选择题

如图所示,倾角为q的光滑斜面足够长,质量为m的物体在沿平行斜面向上的恒力F作用下,由静止从斜面底端沿斜面向上做匀加速直线运动,经过时间t,力F做功为40J,此后撤去力F,物体又经过相同的时间t回到斜面底端,若以地面为重力零势能参考面,则下列说法正确的是

A.物体回到斜面底端的动能为40J

B.恒力F=2mgsinθ

C.撤去力F时,物体的重力势能为30J

D.撤去力F前的运动过程中,物体的动能一直在增加,撤去力F后物体的动能一直在减少

答案

AC

题目分析:对物体从斜面底端沿斜面向上运动经过时间2t回到斜面底端全过程研究,重力做功为零,根据动能定理得,,所以物体回到斜面底端的动能为,故A正确;设撤去F时物体的速度大小为,回到斜面底端时的速度大小为,撤F前物体的加速度大小为,撤F后物体的加速度大小为,撤F前后两个时间内发生的位移大小相等,取沿斜面向上方向为正方向,于是有:,解得:,根据牛顿第二定律得:,解得:,故B错误;根据动能定理得:撤F前有,即,所以撤去力F时,物体的重力势能为,故C正确;撤去力F前的运动过程中,物体向上做匀加速直线运动,撤去F后,物体先向上做减速运动,速度减为零之后,向下加速运动,所以撤去力F后的运动过程中物体的动能是先减小后增加,故D错误。所以选AC。

单项选择题 A1型题
阅读理解

Audrey Hepburn(奥黛丽·赫本)won an Academy Award as Best Actress for her first major American movie, Roman Holiday, which was released in 1953,But she is remem bered as much for her aid work as for her acting.

Born in Belgium in 1929, Audrey’s father was British and her mother was Dutch, Audrey was sent to live at a British school for part of her childhood , During World war ll , she lived and studied in the Netherlands , Her mother thought it would be safe from German attacks ,Audrey studied dance as a teenager and during college when she returned to London after the war, But she realized she wasn’t going to be a ballerina(芭蕾舞女演员),So she began taking acting parts in stage shows, Later she began to get small parts in movies.

But it was Audrey Hepburn’s move to America that brought her true fame ,In 1951 she played the character“Gigi”in the Broadway play of the same name to great critical praise, Two years later, Roman Holiday made her a star at the age of 24.

Audrey make more than 25 movies, Among her most popular roles was Hoolly Golinghtly in Breakfast at Tiffany’s in 1961, There years later she played Eliza Doolittle in my Fair Lady.

She was married two times and had one by each husband, In 1989,the UN Children’s Fund named Audrey a goodwill ambassador, She travelled all over the world in support of UNICEF(联合国儿童基金会) projects ,The UN agency said she was a tireless worker, She often gave 15 interviews a day to gain money and support for UNICEF projects.

Audrey Hepburn often said her loyalty to UNICEF was the result of her experiences as a child during World War II, She said she knew what it was like to be starving and to be saved by international aid , She was a goodwill ambassador until her death in 1993 from colon cancer.

小题1:In Paragraph 1,“her aid work”means       .

A.winning an Academy Award as Best Actress

B.taking acting parts in stage shows

C.making her own movies

D.acting as a goodwill ambassador for UNICEF小题2:The reason why Audrey lived and studied in the Netherlands was that     .

A.she wanted to be a ballerina

B.her parents were from Britain

C.it was safe there

D.the education there was excellent小题3:We can infer from the passage that     .

A.Audrey’s parents lived in Germany during World War II

B.Audrey lived in America in the 1950s

C.Audrey was made to give up dancing

D.the character“Gigi”in the Broadway play was her most popular role小题4:     is NOT mentioned in the passage about Audrey Hepburn

A.Marriage

B.Identity

C.Contribution

D.Religion小题5:     is the right order for Audrey’s life.

①The first time she began to play in movies

②She returned to London from the Netherlands

③She won an Academy Award as Best Actress

④She travelled all over the world in support of UNICEF projects

⑤She played a part in My Fair Lady

A.②①③⑤④

B.①②③⑤④

C.②①⑤③④

D.①②⑤③④