The Earths gravitational force or pull keeps us and everything else on Earth from floating away to space. To get out into space and travel to the moon or other planets we have to overcome the Earths g
The Earth’s gravitational force or pull keeps us and everything else on Earth from floating away to space. To get out into space and travel to the moon or other planets we have to overcome the Earth’s gravitational pull.
Entry into Space
How can we overcome the Earth’s gravitational pull? Scientists have been working on this for a long time. It is only recently that they have been able to build machines powerful enough to get out of the Earth’s gravitational pull. Such machines are called space rockets. Their great speed and power help them to escape from the Earth’s gravitational pull and go into space.
Rockets
The powerful space rocket works along the same lines as a simple firework rocket. The firework rocket has a cylindrical body and a conical head. The body is packed with gunpowder which is the fuel. It is a mixture of chemicals that will burn rapidly to form hot gases.
At the base or foot of the rocket there is an opening or nozzle. A fuse hangs out like a tail from the nozzle. A long stick attached along the body serves to direct the rocket before the fuse is lighted.
When the gunpowder burns, hot gases rush out of the nozzle. The hot gases continue to rush out as long as the gunpowder burns. When these gases shoot downwards through the nozzle the rocket is pushed upwards. This is called jet propulsion. The simple experiment, shown in the picture, will help you to understand jet propulsion.
Topic 2 (选题二)
Basketball Diplomacy
CHINA”S TALLEST SOLDIER never really expected to live the American Dream. But Wang Zhizhi, a 7-foot-1 basketball star from the People’s Liberation Army, is making history as the first Chinese player in the NBA. In his first three weeks in America the 23-year-old rookie has already cashed his first big NBA check, preside over “Wang Zhizhi Day” in San Francisco and become immortalized on his very own trading cards. He’s even played in five games with his new team, the Dallas Mavericks, scoring 24 points in just 38 minutes. Now the affable Lieutenant Wang is joining the Mavericks on their ride into the NBA playoffs — and he is intent on enjoying every minute. One recent evening Wang slipped into the hot tub behind the house of Mavericks assistant coach Donn Nelson. He leaned back, stretched out and pointed at a plane moving across the star-filled sky. In broken English, he started singing his favorite tune: “I believe I can fly. I believe I can touch the sky.”
Back in China, the nation’s other basketball phenom, Yao Ming , can only dream of taking flight. Yao thought he was going to be the first Chinese player in the NBA. The 7-foot-5 Shanghai sensation is more highly touted than Wang: the 20-year-old could be the No.1 overall pick in the June NBA draft. But as the May 13 deadline to enter the draft draws near, Yao is still waiting for a horde of business people and apparatchiks to decide his fate. Last week, as Wang scored 13 points in the Dallas season finale, Yao was wading through a stream of bicycles on a dusty Beijing street.
Yao and Wang are more than just freaks of nature in basketball shorts. The twin towers are national treasures, symbols of China’s growing stature in the world. They’re also emblematic of the NBA’s outsize dreams for conquering China. The NBA, struggling at home, sees salvation in the land of 1.3 billion potential hoop fans. China, determined to win the 2008 Olympics and join the World Trade Organization, is eager to make its mark on the world — on its own terms. The two-year struggle to get these young players into the NBA has been a cultural collision — this one far removed from U.S.-China bickering over spy planes and trade liberalization. If it works out, it could be — in basketball parlance — the ultimate give-and-go. “This is just like Ping-Pong diplomacy,” says Xia Song, a sport-marketing executive who represents Wang. “Only with a much bigger ball.”
Two years ago it looked more like a ball and chain. Wang’s Army bosses were miffed when the Mavericks had the nerve to draft their star back in 1999. Nelson remembers flying to Beijing with the then owner Ross Perot Jr. — son of the eccentric billionaire — to hammer out a deal with the stone-faced communists of the PLA. “You could hear them thinking: ‘What is this NBA team doing, trying to lay claim to our property?’” Nelson recalls. “We tried to explain that this was an honor for Wang and for China.” There was no deal. Wang grew despondent and lost his edge on court.
This year Yao became the anointed one. He eclipsed Wang in scoring and rebounding, and even stole away his coveted MVP award in the Chinese Basketball Association league. It looked as if his Shanghai team — a dynamic semicapitalist club in China’s most open city — would get its star to the NBA first.
（责任编辑:秩名）
