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.
Questions
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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