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The gravity of the moon will not be _____the earth’s.
A. so a strong pull as B. as strong a pull as C. as a strong pull as D. strong a pull than
查看习题详情和答案>>Three hundred and eighty thousand kilometres away from the earth, the moon is man's closest neighbor
in the universe. Its surface is as large as Asia. Though so far away, the moon has a strong influence on the
ecological balance on the earth. For example, partly because of the moon's gravity, our seas and oceans have
tides.
Nearly forty years ago, man's dream of reaching the moon was realized when American astronaut Neil
Armstrong stepped onto the moon's surface. As Armstrong said, it was a small step for a man, but a giant
leap for mankind. Just think of the past when our forebears could hardly find enough to keep alive!
Understanding the moon is of great significance. Since there is no water and no air there, the moon is an
ideal place from which to observe the universe. A huge astronomical telescope has been installed on the moon.
And the moon's solar energy can be used more fully than the earth's. Finally there are the moon's rich mineral
resources. It is no exaggeration to say that the moon is a mini-earth in terms of mineral resources.
Maybe it won't be long before man can benefit from the development of the moon's resources.
B. Tides in the seas and oceans are partly caused by the moon's gravity.
C. The moon's surface is the same as that of Asia.
D. The ecological balance depends on the moon.
B. his step on the moon was not big enough
C. his step on the moon marked man's entrance to a new era (时代) of the moon's research
D. anyone could leave bigger and more steps on the moon than he did
really mean?
the moon to open a new world!
B. Just think that our ancestors (祖先) were working so hard, while we are leading so happy a life!
C. Every time when we think of our hardworking forebears,we can't help feeling shamed of ourselves. How
lazy we are!
D. If you have landed on the moon,you will certainly think of your forefathers, who did a lot in the development
of science.
B. the moon is rich in mineral resources
C. a huge astronomical telescope is more easily installed on the moon than on the earth
D. you can more fully use the solar energy on the moon than on the earth
B. The moon is a likely place to have a lot of diamonds.
C. It is no exaggeration to say that the moon is full of gold and silver as well as all kinds of treasures which
the earth has.
D. The development of the moon's resources will benefit man, but we shall wait a long time.
阅读下列短文，从所给的四个选项中，选出最佳答案
Gravity holds us so close to the earth's surface that nobody can jump more than a few feet into the air with the force of gravity pulling him down．It takes a powerful engine to keep an aeroplane up in the air．If you throw a ball upwards as hard as you can, you will notice that it travels in a curved（弯曲的）path before it comes back to the ground．If the earth had no gravity, the ball, instead of traveling in a curve, would move away in a straight line; in fact, it would never come back to the ground．If the earth were to lose its pull of gravity, we should all fly off it as it spins（旋转）round in space．The earth has a strong pull, but modern rockets going out into space are able to escape from the gravity, because they travel so quickly．With the ball thrown into the air, the height reached by the ball depends upon how hard it is thrown．The greater the starting speed, the higher the ball will go．If it could be thrown so that it travelled fast enough, the ball would escape into space and never come back．Nobody can throw a ball as fast as this, but powerful rocket engines can send spaceships away from the earth at such a speed that the earth's gravity is not able to pull them back．This is how we can now send rockets to the moon．
(1) Gravity holds us close to the earth's surface, and as a result, ______．
[ ]
A．we can lift ourselves no more than a few feet above the earth
B．nobody can jump a few feet into the air
C．no one will be pulled down
D．any one of us can jump as high as expected
(2) If there were no gravity, a ball thrown upwards would ______．
[ ]
A．spin round in space
B．fall in a curved path
C．fly off into space
D．move towards the earth
(3) The ball thrown into the air would never come back to the ground ______．
[ ]
A．without a powerful push
B．if it were thrown upwards as hard as you can
C．should it travel in a curved path
D．were it not for gravity
(4) The height the ball will reach depends on ______．
[ ]
A．the escape speed
B．its starting speed
C．the limiting speed
D．its traveling speed
(5) What is it that makes it possible to put a spaceship into orbit（轨道）?
[ ]
A．The earth's gravity
B．A powerful engine
C．A strong pull
D．The powerful rocket engine
查看习题详情和答案>>(江西省抚州一中2009届高三第四次模拟考试B篇)
How many things can you see in the night sky? A lot! On a clearnight you might see the Moon, some planets, and thousands of sparkling stars.
You can see even more with a telescope. And with bigger and bigger telescopes you can see more and more objects in the sky. And you can see those objects in more and more detail.
But scientists believe there are some things in the sky that we will never see. We won't see them with the biggest telescope in the world, on the clearest night of the year.
That's because they're invisible. They're the mysterious dead stars called black holes.
You might find it hard to imagine that stars die. After all, our Sun is a star. Year after year we see it up in the sky, burning brightly, giving us heat and light. The Sun certainly doesn't seem to be getting old or weak. But stars do burn out and die after billions of years.
As a star's gases burn, they give off light and heat. But when the gas runs out, the star stops burning and begins to die.
As the star cools, the outer layers of the star pull in toward the center. The star squashes into a smaller and smaller ball. If the star was very small, the star ends up as a cold, dark ball called a black dwarf. If the star was very big, it keeps squashing inward until it's packed together tighter than anything in the universe.
Imagine if the Earth were crushed until it was the size of a tiny marble. That's how tightly this dead star, a black hole, is packed. What pulls the star in toward its center with such power? It's the same force that pulls you down when you jump--the force called gravity. A black hole is so tightly packed that its gravity sucks in everything--even light. The light from a black hole can never come back to your eyes. That's why you see nothing but blackness.
So next time you stare up at the night sky, remember: there's more in the Sky than we can see! Scattered in the silent darkness are black holes--the great mystery of space.
60. According to the article, what causes a star to die?
A. As its gases run out, it cools down. B. It has a collision with other stars.
C. It can only live for about a million years.
D. As it gets hotter and hotter, it explodes.
61. Which of the following statements is NOT true?
A. Black holes are dead stars.
B. Black holes have gravity.
C. Black holes are invisible.
D. There is nothing as mysterious as a black hole.
62. W. hat happens AFTER a star dies?
A. It becomes invisible. B. It fails to Earth.
C. It burns up all of its gases. D. It becomes brighter and easier to see.
63. Why can't you see light when you look at a black hole?
A. Because most black holes are so far away.
B. Because the gravity of a black hole is so strong that it sucks the light inward.
C. Because as the star's gases burn, it stops giving off heat and light.
D. Because as a star cools, its outer layers pull in toward its center.
查看习题详情和答案>>How many things can you see in the night sky? A lot! On a clear night you might see the Moon, some planets, and thousands of sparkling stars.
You can see even more with a telescope. And with bigger and bigger telescopes you can see more and more objects in the sky. And you can see those objects in more and more detail.
But scientists believe there are some things in the sky that we will never see. We won't see them with the biggest telescope in the world, on the clearest night of the year.
That's because they're invisible. They're the mysterious dead stars called black holes.
You might find it hard to imagine that stars die. After all, our Sun is a star. Year after year we see it up in the sky, burning brightly, giving us heat and light. The Sun certainly doesn't seem to be getting old or weak. But stars do burn out and die after billions of years.
As a star's gases burn, they give off light and heat. But when the gas runs out, the star stops burning and begins to die.
As the star cools, the outer layers of the star pull in toward the center. The star squashes into a smaller and smaller ball. If the star was very small, the star ends up as a cold, dark ball called a black dwarf. If the star was very big, it keeps squashing inward until it's packed together tighter than anything in the universe.
Imagine if the Earth were crushed until it was the size of a tiny marble. That's how tightly this dead star, a black hole, is packed. What pulls the star in toward its center with such power? It's the same force that pulls you down when you jump--the force called gravity. A black hole is so tightly packed that its gravity sucks in everything--even light. The light from a black hole can never come back to your eyes. That's why you see nothing but blackness.
So next time you stare up at the night sky, remember: there's more in the Sky than we can see! Scattered in the silent darkness are black holes--the great mystery of space.
68. According to the article, what causes a star to die?
A. As its gases run out, it cools down. B. It has a collision with other stars.
C. It can only live for about a million years. D. As it gets hotter and hotter, it explodes.
69. Which of the following statements is NOT true?
A. Black holes are dead stars. B. Black holes have gravity.
C. Black holes are invisible. D. There is nothing as mysterious as a black hole.
70. What happens AFTER a star dies?
A. It becomes invisible. B. It fails to Earth.
C. It burns up all of its gases. D. It becomes brighter and easier to see.
71. Why can't you see light when you look at a black hole?
A. Because most black holes are so far away.
B. Because the gravity of a black hole is so strong that it sucks the light inward.
C. Because as the star's gases burn, it stops giving off heat and light.
D. Because as a star cools, its outer layers pull in toward its center.
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