The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biologists long regarded it as an example of adaptation by natural selection, but for physicists it bordered on the miraculous.
Line Newton's laws of motion assume that the total amount of spin of a body cannot change (5) unless an external torque speeds it up or slows it down. If a cat has no spin when it is released and experiences no external torque, it ought not to be able to twist around as it falls.
In the speed of its execution, the righting of a tumbling cat resembles a magician's trick. The gyrations of the cat in midair are too fast for the human eye to follow, so the (10) process is obscured. Either the eye must be speeded up, or the cat's fall slowed down for the phenomenon to be observed. A century ago the former was accomplished by means of high-speed photography using equipment now available in any pharmacy. But in the nineteenth century the capture on film of a falling cat constituted a scientific experiment.
(15)The experiment was described in a paper presented to the Paris Academy in 1894.
Two sequences of twenty photographs each, one from the side and one from behind,
show a white cat in the act of righting itself. Grainy and quaint though they are, the
photos show that the cat was dropped upside down, with no initial spin, and still landed on its feet. Careful analysis of the photos reveals the secret ; As the cat rotates the front(20) of its body clockwise, the rear and tail twist counterclockwise, so that the total spin remains zero, in perfect accord with Newton's laws. Halfway down, the cat pulls in its legs before reversing its twist and then extends them again, with the desired end result.
The explanation was that while no body can acquire spin without torque, a flexible one can readily change its orientation, or phase. Cats know this instinctively, but scientists(25) could not be sure how it happened until they increased the speed of their perceptions a thousandfold.
31. What does the passage mainly discuss?
(A) The explanation of an interesting phenomenon
(B) Miracles in modern science
(C) Procedures in scientific investigation
(D) The differences between biology and physics
32. The word “process”in line 10 refers to
(A) the righting of a tumbling cat
(B) the cat's fall slowed down
(C) high-speed photography
(D) a scientific experiment
33. Why are the photographs mentioned in line 16 referred to as an “experiment”?
(A) The photographs were not very clear.
(B) The purpose of the photographs was to explain the process.
(C) The photographer used inferior equipment.
(D) The photographer thought the cat might be injured.
34. Which of the following can be inferred about high-speed photography in
the late 1800's ?
(A) It was a relatively new technology.
(B) The necessary equipment was easy to obtain.
(C) The resulting photographs are difficult to interpret.
(D) It was not fast enough to provide new information.
35. The word “rotates” in line 19 is closest in meaning to
(A) drops
(B) turns
(C) controls
(D) touches
36. According to the passage, a cat is able to right itself in midair because it is
(A) frightened
(B) small
(C) intelligent
(D) flexible
37. The word “readily”in line 24 is closest in meaning to
(A) only
(B) easily
(C) slowly
(D) certainly
38. How did scientists increase “the speed of their perceptions a
thousandfold”(lines 25-26)?
(A) By analyzing photographs
(B) By observing a white cat in a dark room
(C) By dropping a cat from a greater height
(D) By studying Newton's laws of motion
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