问题 计算题

质量为10kg的物体放在水平桌面上以16m/s的初速度向右运动, 物体受到一个水平向右的拉力F=50N和水平向左的阻力f=30N,(g取10m/s2.)求:

(1)物体滑行过程中的加速度大小和方向?

(2)物体滑行至2s末的速度多大?

(3)若撤去水平向右的力F, 2s内物体的位移多少?

答案

(1)     方向与F的方向相同  (2) 20m/s   (3) 26m

题目分析:(1)对物体进行受力分析,根据牛顿第二定律的,解得,方向与F的方向相同

(2)由运动学公式得v=20m/s

(3) 撤去水平向右的力F后,合外力为f,由牛顿第二定律的

由运动学公式得x=26m

点评:本题属于已知物体的受力情况,由牛顿第二定律求出物体的加速度,再通过运动学公式就可以确定物体的运动情况.加速度是联系运动和力的纽带、桥梁.

阅读理解

Do you know what Oscar is? When did it start? Maybe you can find the background of the awards in the following passage.

The awards started in 1929. Their full title is “The Academy of Motion Picture Arts and Sciences Awards”. The Academy is a group of people who have worked in the film industry for many years. They decide who will receive the awards. The awards are often referred to as the “Oscar”. This is a nickname given to the awards by a lady called Margaret Herrick. She was once the director of the Academy and she once said that the little gold statue(雕像) reminded her of her uncle Oscar!

The Oscar is always an exciting event. Each year, at least one unusual thing happens. When the Italian actor and director Roberto Benigni won an Oscar for best foreign film, he danced on stage! When Gwyneth Paltrow, the star of Shakespeare in Love won the Oscar for best actress, she could not make her acceptance speech because she was crying so much with happiness!

In 1987, Roberto Benigni won the award for best director for a film about the last emperor of China. Since then, Chinese film and actors have started to make an impact at the award. Crouching Tiger, Hidden Dragon was a huge success and it won the award for best foreign language film in 2001. It also won several technical awards for its amazing “flying” people. We expect to see more awards for Chinese film in the near future.

It’s time for the Oscar again. Once more, the stars will dress up in their finest and go to Kodak Theater. There, they will find out who had won the awards for best actor, best actress and best director. Millions of people watch the awards every year to find out who the winners are. Some people watch it to see the stars crying and laughing as they receive their awards.

小题1:Who give the awards?

A.In 1927.

B.Oscar.

C.The Academy of Nicknames.

D.A group of people who have worked in the film industry for many years.小题2:What did Gwyneth Paltrow win an Oscar for?

A.Best Director.

B.Best Foreign Film.

C.Best Actress.

D.Best Actor.小题3:Which Chinese film won an award for best foreign film?

A.Crouching Dragon, Hidden Tiger.

B.Crouching and Hidden Dragon and Tiger.

C.Crouching Tiger, Hidden Dragon.

D.Crouching, Dragon, Hiding Tiger.小题4: Where are the Oscars held?

A.At the Academy.

B.in a Los Angeles restaurant.

C.At Oscar’s house.

D.At Kodak Theater.小题5:Why do some people watch Oscars?

A.To see the restaurant.

B.To see the fashion.

C.To see a film.

D.To see the stars crying and laughing.

多项选择题