IV.阅读理解（共17小题；每小题２分，满分34分）

Like cats, geckos（壁虎）always land on their feet. If they happen to fall from a wall or leaf they’ve been climbing, a quick move of the tail makes sure that they always land on their feet first, a new study finds.

Geckos are truly built for climbing: their feet have hairy toes that can fix themselves to a wall or other vertical（竖直的）surfaces. However, geckos’ feet can’t always keep hold and they may fall to the ground. When geckos fall or jump off a wall, they always land stomach-side down. Geckos’ long tails become necessary during their falls, the new study shows.

Researchers did an experiment. They placed geckos up-side-down on the underside of a leaf. When they lost their foothold and fell, the geckos pitched （倾斜）their tails for balance. They then rotated（旋转）their tails to make their bodies rotate. As soon as they were right-side up, they stopped rotating. On average, it only took the geckos about a tenth of a second to right themselves so that they would land on their feet.

Cats use a different way to land on their feet after a fall. As their tails don’t have the power like geckos’ tails, cats can’t use them to right themselves. Instead they twist their bodies around mid-air.

Engineers are trying to build a robot that imitates the geckos’ climbing ability. A tail will be fixed to the robot to allow it to keep balance.

54. What do we know about geckos?

A. Their toes make it possible for them to walk on walls.

B. Their tails can fix them to a wall or other vertical surfaces.

C. They often land on their backs when they jump off walls.

D. It takes them a second to right themselves in mid-air.

55. How do cats avoid their injury during a fall?

A. By twisting their bodies.                 B. By fixing their toes to the ground.

C. By using their tails to right themselves.        D. By landing upside-down.

56. Geckos’ special abilities have given engineers some new ideas to _________.

A. allow robots to climb vertical surfaces       

B. reproduce geckos like robots

C. invent robots that can rotate on the ground

D. invent robots that can balance themselves using their tails

57. What is the text mainly talking about?

A. The interesting living habits of geckos.   B. The differences between cats and geckos.

C. Why geckos always land on their feet.      D. How geckos climb up vertical walls.

IV.阅读理解（共17小题；每小题２分，满分34分）
Like cats, geckos（壁虎）always land on their feet. If they happen to fall from a wall or leaf they’ve been climbing, a quick move of the tail makes sure that they always land on their feet first, a new study finds.
Geckos are truly built for climbing: their feet have hairy toes that can fix themselves to a wall or other vertical（竖直的）surfaces. However, geckos’ feet can’t always keep hold and they may fall to the ground. When geckos fall or jump off a wall, they always land stomach-side down. Geckos’ long tails become necessary during their falls, the new study shows.
Researchers did an experiment. They placed geckos up-side-down on the underside of a leaf. When they lost their foothold and fell, the geckos pitched （倾斜）their tails for balance. They then rotated（旋转）their tails to make their bodies rotate. As soon as they were right-side up, they stopped rotating. On average, it only took the geckos about a tenth of a second to right themselves so that they would land on their feet.
Cats use a different way to land on their feet after a fall. As their tails don’t have the power like geckos’ tails, cats can’t use them to right themselves. Instead they twist their bodies around mid-air.
Engineers are trying to build a robot that imitates the geckos’ climbing ability. A tail will be fixed to the robot to allow it to keep balance.
54. What do we know about geckos?
A. Their toes make it possible for them to walk on walls.
B. Their tails can fix them to a wall or other vertical surfaces.
C. They often land on their backs when they jump off walls.
D. It takes them a second to right themselves in mid-air.
55. How do cats avoid their injury during a fall?
A. By twisting their bodies.                 B. By fixing their toes to the ground.
C. By using their tails to right themselves.        D. By landing upside-down.
56. Geckos’ special abilities have given engineers some new ideas to _________.
A. allow robots to climb vertical surfaces       
B. reproduce geckos like robots
C. invent robots that can rotate on the ground
D. invent robots that can balance themselves using their tails
57. What is the text mainly talking about?
A. The interesting living habits of geckos.   B. The differences between cats and geckos.
C. Why geckos always land on their feet.      D. How geckos climb up vertical walls.

The Parthenon is an ancient Greek temple built in Athens about 438 B. C. Many people think that the Parthenon is one of the world' s most beautiful buildings. It has a grace and balance that have pleased the eyes of man for centuries.
Architects who have studied the Parthenon know that the Parthenon is a giant optical illusion. An optical illusion is a trick our eyes play on us. All the seemingly straight lines of the Parthenon are actually curves(rounded bends). These curves did not happen by accident. The ancient Greeks,who were fine engineers as well as excellent artists, knew that straight lines can sometimes appear to be curved ! So they designed their columns (stone poles) to look straight.
Try drawing two long parallel(平行)lines on paper. Do they seem to look closer together in the middle than at the ends? A tall column is likely to look narrow halfway up, too. The columns of the Parthenon look as if they stand perfectly straight. Actually, they are slightly bigger in size in the middle and go inward a little at the top. If lines were drawn up along opposite sides of the columns, these lines would meet about one mile above the building.
A platform of three steps forms the base on which the Parthenon rests.These steps have strong horizontal(水平)lines that balance the vertical(竖直)lines of the columns.But the steps are not really level and flat!They curve up in the middle because if they were absolutely straight,,they would appear to curve down.The line of the top step,if continued at both ends,would form a circle with a radius of 3. 5 miles.
When is a curved line not a curved line? When our eyes tell us it is straight!
73.The passage mainly tells us_______.      
A. what two parallel lines look like on paper
B. why a curved line can appear to be straight
C. where the secret of the Parthenon Temple lies
D. when the columns of the Parthenon look curved
74.Which of the following is close in shape with the steps of the platform?
A.                B.           C.       D.
75.What can we infer from the passage?
A. The Parthenon is a famous historic building.
B. The Greeks knew a lot about optical illusions.
C. The ancient Greeks were people of intelligence.
D. Curved lines can meet somewhere above a building.

如图所示，竖直平面内的3/4圆弧形光滑轨道半径为R，A端与圆心O等高，AD为与水平方向成45°角的斜面，B端在O的正上方，一个可看成质点的小球在A点正上方由静止开始释放，自由下落至A点后进入圆形轨道并恰能到达B点。求：

（1）到达B点的速度大小；

（2）释放点距A点的竖直高度；

（3）小球落到斜面上C点时的速度大小。

如图所示，竖直平面内的3/4圆弧形光滑轨道半径为R，A端与圆心O等高，AD为与水平方向成45°角的斜面，B端在O的正上方，一个可看成质点的小球在A点正上方由静止开始释放，自由下落至A点后进入圆形轨道并恰能到达B点。求：

（1）到达B点的速度大小；

（2）释放点距A点的竖直高度；

（3）小球落到斜面上C点时的速度大小。