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Updated on: 03 Aug 2019, 03:59
Originally posted by SouthCity on 30 Jul 2016, 22:07.
Last edited by Sajjad1994 on 03 Aug 2019, 03:59, edited 1 time in total.
Last edited by Sajjad1994 on 03 Aug 2019, 03:59, edited 1 time in total.
Updated complete topic (58).
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Question 1
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
85%
(hard)
Question Stats:
41% (03:21) correct
59%
(03:42) wrong
based on 4135
sessions
History
Date
Time
Result
Not Attempted Yet
Question 2
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
67% (00:55) correct 33%
(01:13) wrong
based on 4581
sessions
History
Date
Time
Result
Not Attempted Yet
Question 3
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
64% (01:14) correct 36%
(01:30) wrong
based on 4500
sessions
History
Date
Time
Result
Not Attempted Yet
Question 4
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
56% (01:12) correct 44%
(01:28) wrong
based on 4373
sessions
History
Date
Time
Result
Not Attempted Yet
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 the 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.
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 the 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.
1. 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.
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.
2. According to the passage, the use of Shortt clocks led to the discovery that
A) optical sensing equipment can be used effectively in time-keeping 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
A) optical sensing equipment can be used effectively in time-keeping 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
3. 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
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
4. 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.
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.
21 Jul 2018, 05:17
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Hi sandman13
#1 is a pretty tough inference question. But we get our evidence for C from the very first sentence:
Sometimes it can be tempting to fly through the first sentence or two as you're thinking "what's this passage REALLY about?" But there can be important info in that very first sentence - here it's the word ultimate. As the passage goes on, we can understand that ultimate must mean it's the very best of its kind. Here, best of its kind seems to mean stable and accurate. When researchers want to measure how good the Shortt clocks are, they have to compare them to atomic clocks.
You're right that C is extreme. Keep in mind that you CAN choose an extreme answer if the passage itself gives you extreme evidence. Here "ultimate" is our extreme evidence, so you can justify C.
Things to take away: 1) Read carefully starting with the very first sentence. 2) Always be sensitive to extreme language in the passage (best, worst, first, last, etc) because it could help you justify an extreme answer later.
Does this help? Let us know.
Best, Jenn
#1 is a pretty tough inference question. But we get our evidence for C from the very first sentence:
Quote:
Sometimes it can be tempting to fly through the first sentence or two as you're thinking "what's this passage REALLY about?" But there can be important info in that very first sentence - here it's the word ultimate. As the passage goes on, we can understand that ultimate must mean it's the very best of its kind. Here, best of its kind seems to mean stable and accurate. When researchers want to measure how good the Shortt clocks are, they have to compare them to atomic clocks.
You're right that C is extreme. Keep in mind that you CAN choose an extreme answer if the passage itself gives you extreme evidence. Here "ultimate" is our extreme evidence, so you can justify C.
Things to take away: 1) Read carefully starting with the very first sentence. 2) Always be sensitive to extreme language in the passage (best, worst, first, last, etc) because it could help you justify an extreme answer later.
Does this help? Let us know.
Best, Jenn
23 Feb 2018, 08:18
Kudos
Bookmarks
1. 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
Info not stated in the passage.
B) Atomic clocks depend on the operation of
mechanisms that were invented by William Shortt
and first used in the Shortt clock.
Info not stated in the passage.
C) No type of clock that keeps time more stably and
accurately than a Shortt clock relies fundamentally on
the operation of a pendulum.
Correct. The relevant part of th passage is:
The ultimate pendulum clock, indeed the ultimate
mechanical clock of any kind, was invented by a British
engineer, William Shortt.
D) Subtle changes in the earth's rotation slightly reduce
the accuracy of all clocks used in observatories after
1921.
Info not stated in the passage.
E) At least some mechanical clocks that do not have
pendulums are almost identical to Shortt clocks in
their mode of operation.
Info not stated in the passage.
2. According to the passage, the use of Shortt clocks
led to the discovery that
The relevant part of the passage is:
“The first indications of seasonal variations in
the earth's rotation were gleaned by the use of Shortt
clocks.”
A)optical sensing equipment can be used effectively in
time-keeping systems
Info not stated in the passage and not in the relevant part
B) atomic clocks can be used in place of pendulum
clocks in observatories
Info not stated in the passage and not in the relevant part
C) tides occur in solid ground as well as in oceans
Info not in the relevant part
D) the earth's rotation varies from one time of year to another
Correct. Words equivalent to relevant part in the passage
Seasonal variations = varies from one time of year to another
E) pendulums can be synchronized with one another electronically
Info not in the relevant part
3. The passage most strongly suggests that the study described in the third paragraph would not have been possible in the absence of
Relevant part of the passage is:
“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.”
A) accurate regarding the times at which high and low ocean tides occurred at various locations during 1984
Info not stated in the passage or the relevant part
B) comparative data regarding the use of Shortt clocks in observatories between 1921 and 1932
Info not stated in the passage or the relevant part
C) a non-Shortt clock that was known to keep time extremely precisely and reliably
Correct.
“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.”
Strongly suggests that an extremely precise non-shortt clock is needed
D) an Innovative electric-power source that was not available in the 1920s and 1930s
Info not stated in the passage or the relevant part
E) optical data-transmission devices to communicate between the U.S. Naval Observatory and other research facilities
“between the U.S. Naval Observatory and other research facilities” not stated in the relevant part.
4. 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?
The relevant part is the first para:
“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.”
A) It contained elaborate mechanisms that were
attached to, and moved by, the pendulum.
Question is inference and so not directly stated
“via an elaborate electromechanical
linkage, the primary pendulum ensured that the”
“via” does not suggest any attachment to or their movement due to the pendulum.
B) It was firmly sealed during normal operation of the
clock.
Correct. The relevant part is:
“The primary pendulum swung freely in a vacuum chamber.”
Equivalent meaning : vacuum chamber and strongly sealed
C) It was at least partly transparent so as to allow for
certain types of visual data output.
Info not in the relevant part
D) It housed both the primary pendulum and another
pendulum.
Wrong Info
E) It contained a transmitter that was activated at
irregular intervals to send a signal to the secondary
pendulum.
Info not in the relevant part
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
Info not stated in the passage.
B) Atomic clocks depend on the operation of
mechanisms that were invented by William Shortt
and first used in the Shortt clock.
Info not stated in the passage.
C) No type of clock that keeps time more stably and
accurately than a Shortt clock relies fundamentally on
the operation of a pendulum.
Correct. The relevant part of th passage is:
The ultimate pendulum clock, indeed the ultimate
mechanical clock of any kind, was invented by a British
engineer, William Shortt.
D) Subtle changes in the earth's rotation slightly reduce
the accuracy of all clocks used in observatories after
1921.
Info not stated in the passage.
E) At least some mechanical clocks that do not have
pendulums are almost identical to Shortt clocks in
their mode of operation.
Info not stated in the passage.
2. According to the passage, the use of Shortt clocks
led to the discovery that
The relevant part of the passage is:
“The first indications of seasonal variations in
the earth's rotation were gleaned by the use of Shortt
clocks.”
A)optical sensing equipment can be used effectively in
time-keeping systems
Info not stated in the passage and not in the relevant part
B) atomic clocks can be used in place of pendulum
clocks in observatories
Info not stated in the passage and not in the relevant part
C) tides occur in solid ground as well as in oceans
Info not in the relevant part
D) the earth's rotation varies from one time of year to another
Correct. Words equivalent to relevant part in the passage
Seasonal variations = varies from one time of year to another
E) pendulums can be synchronized with one another electronically
Info not in the relevant part
3. The passage most strongly suggests that the study described in the third paragraph would not have been possible in the absence of
Relevant part of the passage is:
“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.”
A) accurate regarding the times at which high and low ocean tides occurred at various locations during 1984
Info not stated in the passage or the relevant part
B) comparative data regarding the use of Shortt clocks in observatories between 1921 and 1932
Info not stated in the passage or the relevant part
C) a non-Shortt clock that was known to keep time extremely precisely and reliably
Correct.
“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.”
Strongly suggests that an extremely precise non-shortt clock is needed
D) an Innovative electric-power source that was not available in the 1920s and 1930s
Info not stated in the passage or the relevant part
E) optical data-transmission devices to communicate between the U.S. Naval Observatory and other research facilities
“between the U.S. Naval Observatory and other research facilities” not stated in the relevant part.
4. 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?
The relevant part is the first para:
“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.”
A) It contained elaborate mechanisms that were
attached to, and moved by, the pendulum.
Question is inference and so not directly stated
“via an elaborate electromechanical
linkage, the primary pendulum ensured that the”
“via” does not suggest any attachment to or their movement due to the pendulum.
B) It was firmly sealed during normal operation of the
clock.
Correct. The relevant part is:
“The primary pendulum swung freely in a vacuum chamber.”
Equivalent meaning : vacuum chamber and strongly sealed
C) It was at least partly transparent so as to allow for
certain types of visual data output.
Info not in the relevant part
D) It housed both the primary pendulum and another
pendulum.
Wrong Info
E) It contained a transmitter that was activated at
irregular intervals to send a signal to the secondary
pendulum.
Info not in the relevant part
