问题 问答题

我国自主研发的涡浆支线飞机“新舟600”,试飞成功,填补了我国航空史上的一个空白,试飞中,若飞机以500km/h的速度水平匀速飞行了1.2h,飞机质量为20t.(g=10N/kg)

(1)飞机水平飞行的路程是多少?

(2)飞机水平飞行时受到的升力是多大?

(3)飞机着陆后水平运动,轮子与地面接触的总面积约为1.5m2,飞机对地面的压强是多大?

答案

(1)飞机水平飞行的路程:

s=vt=500km/h×1.2h=600km;

(2)飞机的质量:

m=20t=2×104kg,

飞机重:

G=mg=2×10 4kg×10N/kg=2×105N,

∵飞机水平匀速飞行,

∴飞机在竖直方向上受到的重力和受到的升力是一对平衡力,

∴飞机水平飞行时受到的升力:

F=G=2×105N;

(3)飞机着陆后对地面的压强:

p=

F
s
=
G
s
=
105N
1.5m2
≈1.3×105Pa.

答:(1)飞机水平飞行的路程是600km;

(2)飞机水平飞行时受到的升力是2×105N;

(3)飞机着陆后对地面的压强是1.3×105Pa.

选择题
单项选择题

Jack’s friend Tony had recently gotten a tattoo (纹身), and Jack was so impressed by Tony’s bravery and his tattoo that he decided to get one too. Why do a lot of young people in North America get tattoos today Peer pressure, media influence, and personal expression are some of the common reasons.
The desire to be part of a group, to be accepted by one’s friends or peers, can have a great influence on what a person does. Sometimes, wearing a tattoo can be a sign that you belong to a certain group. Gangs often use special clothes and tattoos to identify their particular group. For example, in one gang all the members may wear green army jackets and have large "Xs" tattooed on their arms. It is not only gangs that have this type of special "uniform". Young people often belong to a certain group of friends. Some of these groups wear only brand-name clothes. Others wear tattoos. When a person’s friends are all doing something, such as getting a tattoo, that person is more likely to do the same thing, and get a tattoo too.
The media is another big influence behind the popularity of tattoos in North America. A wide variety of media images show tattoos. Tattoos can be seen on people appearing in commercials selling expensive cars. Famous sports heroes with tattoos are shown in magazines. Fashion models are often seen in magazines and on TV wearing designer clothes that show their bodies tattooed with detailed and colorful patterns. These media images link tattoos to ideas of wealth, success, and status. As a result, many people decide to get a tattoo for its fashion and status value.
It is not always the influence of other people or the media that results in a person getting a tattoo. Many people decide to wear tattoos in order to express their artistic nature, their beliefs, or their feelings -- in other words, to show their individuality. A musician in a rock band may get a tattoo of a guitar on the arm. Some environmentalists may tattoo pictures of endangered animals on their shoulders. Lovers may tattoo each others’ names over their hearts. A tattoo can be a public sign to show what is important in a person’s life.

Which of the following groups of people are seen wearing tattoos in the media

A. Sports Stars.
B. Car sellers.
C. Fashion designers.
D. Movie stars.