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lavanya.18
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26 Sep 2024, 07:12
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The ultimate pendulum clock, indeed the ultimate
mechanical clock of any kind, was invented by a British
engineer, William Shortt. The first was installed in the
Royal Observatory in Edinburgh in 1921. The Shortt
clock had two pendulums, primary and secondary. The
primary pendulum swung freely in a vacuum chamber. Its
only job was to synchronize the swing of the secondary
pendulum, which was housed in a neighboring cabinet
and drove the time-indicating mechanism. Every 30
seconds, the secondary pendulum sent an electrical
signal to give a nudge to the primary pendulum. In
return, via an elaborate electromechanical linkage, the
primary pendulum ensured that the secondary pendulum
never got out of step.
Shortt clocks were standard provision in
astronomical observatories of the 1920s and 1930s
and are credited with keeping time to better than two
milliseconds in a day. Many were on record as losing
or gaining no more than one second in a year—a
stability of one part in 30 million. The first indications
of seasonal variations in the earth’s rotation were
gleaned by the use of Shortt clocks.
In 1984, Pierre Boucheron carried out a study of
a Shortt clock which had survived in the basement
of the United States Naval Observatory since 1932.
After replacing the electromechanical linkage with
modern optical sensing equipment, he measured the
Shortt clock’s rate against the observatory’s atomic
clocks for a month. He found that it was stable to 200
microseconds a day over this period, equivalent to two
to three parts in a billion. What is more, the data also
revealed that the clock was responding to the slight
tidal distortion of the earth due to the gravitational pull
of the moon and sun.
In addition to causing the familiar ocean tides,
both the sun and the moon raise tides in the solid
body of the earth. The effect is to raise and lower the
surface of the earth by about 30 centimeters. Since
the acceleration due to gravity depends on distance
from the center of the earth, this slight tidal movement
affects the period of swing of a pendulum. In each
case, the cycle of the tides caused the clock to gain
or lose up to 140 microseconds.
Q1) According to the passage, the use of Shortt clocks led to the discovery that
A. optical sensing equipment can be used effectively in timekeeping systems
B. atomic clocks can be used in place of pendulum clocks in observatories
C. tides occur in solid ground as well as in oceans
D. the earth’s rotation varies from one time of year to another
E. pendulums can be synchronized with one another electronically
Q2) The passage most strongly suggests that which of the following is true of the chamber in
which a Shortt clock’s primary pendulum was housed?
A. It contained elaborate mechanisms that were attached to, and moved by, the pendulum.
B. It was firmly sealed during normal operation of the clock.
C. It was at least partly transparent so as to allow for certain types of visual data output.
D. It housed both the primary pendulum and another pendulum.
E. It contained a transmitter that was activated at irregular intervals to send a signal to the
secondary pendulum.
Q3) The passage most strongly suggests that its author would agree with which of the following
statements about clocks?
A. Before 1921, no one had designed a clock that used electricity to aid in its timekeeping
functions.
B. Atomic clocks depend on the operation of mechanisms that were invented by William
Shortt and first used in the Shortt clock.
C. No type of clock that keeps time more stably and accurately than a Shortt clock relies
fundamentally on the operation of a pendulum.
D. Subtle changes in the earth’s rotation slightly reduce the accuracy of all clocks used in
observatories after 1921.
E. At least some mechanical clocks that do not have pendulums are almost identical to
Shortt clocks in their mode of operation.
Q4) The passage most strongly suggests that the study described in the third paragraph would not
have been possible in the absence of
A. accurate information regarding the times at which high and low ocean tides occurred at
various locations during 1984
B. comparative data regarding the use of Shortt clocks in observatories between 1921 and
1932
C. a non-Shortt clock that was known to keep time extremely precisely and reliably
D. an innovative electric-power source that was not available in the 1920s and 1930s
E. optical data-transmission devices to communicate between the U.S. Naval Observatory
and other research facilities
mechanical clock of any kind, was invented by a British
engineer, William Shortt. The first was installed in the
Royal Observatory in Edinburgh in 1921. The Shortt
clock had two pendulums, primary and secondary. The
primary pendulum swung freely in a vacuum chamber. Its
only job was to synchronize the swing of the secondary
pendulum, which was housed in a neighboring cabinet
and drove the time-indicating mechanism. Every 30
seconds, the secondary pendulum sent an electrical
signal to give a nudge to the primary pendulum. In
return, via an elaborate electromechanical linkage, the
primary pendulum ensured that the secondary pendulum
never got out of step.
Shortt clocks were standard provision in
astronomical observatories of the 1920s and 1930s
and are credited with keeping time to better than two
milliseconds in a day. Many were on record as losing
or gaining no more than one second in a year—a
stability of one part in 30 million. The first indications
of seasonal variations in the earth’s rotation were
gleaned by the use of Shortt clocks.
In 1984, Pierre Boucheron carried out a study of
a Shortt clock which had survived in the basement
of the United States Naval Observatory since 1932.
After replacing the electromechanical linkage with
modern optical sensing equipment, he measured the
Shortt clock’s rate against the observatory’s atomic
clocks for a month. He found that it was stable to 200
microseconds a day over this period, equivalent to two
to three parts in a billion. What is more, the data also
revealed that the clock was responding to the slight
tidal distortion of the earth due to the gravitational pull
of the moon and sun.
In addition to causing the familiar ocean tides,
both the sun and the moon raise tides in the solid
body of the earth. The effect is to raise and lower the
surface of the earth by about 30 centimeters. Since
the acceleration due to gravity depends on distance
from the center of the earth, this slight tidal movement
affects the period of swing of a pendulum. In each
case, the cycle of the tides caused the clock to gain
or lose up to 140 microseconds.
Q1) According to the passage, the use of Shortt clocks led to the discovery that
A. optical sensing equipment can be used effectively in timekeeping systems
B. atomic clocks can be used in place of pendulum clocks in observatories
C. tides occur in solid ground as well as in oceans
D. the earth’s rotation varies from one time of year to another
E. pendulums can be synchronized with one another electronically
Q2) The passage most strongly suggests that which of the following is true of the chamber in
which a Shortt clock’s primary pendulum was housed?
A. It contained elaborate mechanisms that were attached to, and moved by, the pendulum.
B. It was firmly sealed during normal operation of the clock.
C. It was at least partly transparent so as to allow for certain types of visual data output.
D. It housed both the primary pendulum and another pendulum.
E. It contained a transmitter that was activated at irregular intervals to send a signal to the
secondary pendulum.
Q3) The passage most strongly suggests that its author would agree with which of the following
statements about clocks?
A. Before 1921, no one had designed a clock that used electricity to aid in its timekeeping
functions.
B. Atomic clocks depend on the operation of mechanisms that were invented by William
Shortt and first used in the Shortt clock.
C. No type of clock that keeps time more stably and accurately than a Shortt clock relies
fundamentally on the operation of a pendulum.
D. Subtle changes in the earth’s rotation slightly reduce the accuracy of all clocks used in
observatories after 1921.
E. At least some mechanical clocks that do not have pendulums are almost identical to
Shortt clocks in their mode of operation.
Q4) The passage most strongly suggests that the study described in the third paragraph would not
have been possible in the absence of
A. accurate information regarding the times at which high and low ocean tides occurred at
various locations during 1984
B. comparative data regarding the use of Shortt clocks in observatories between 1921 and
1932
C. a non-Shortt clock that was known to keep time extremely precisely and reliably
D. an innovative electric-power source that was not available in the 1920s and 1930s
E. optical data-transmission devices to communicate between the U.S. Naval Observatory
and other research facilities
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26 Sep 2024, 07:17
Kudos
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lavanya.18
This question is discussed here: https://gmatclub.com/forum/the-ultimate ... 22910.html
Hope it helps.
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Reading Comprehension (RC) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
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