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The ultimate pendulum clock, indeed the ultimate mechanical clock of a

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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
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1. Inference
P1: 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.
P1: Every 30 seconds the secondary pendulum sent an electrical signal to give a nudge to the primary pendulum.
Inference flip: A. Before 1921 no one had designed a clock that used electricity to aid in its timekeeping functions.

2. According to passage:
P1: The ﬁrst indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks.
P3: 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.
ANS: C

3. Inference (Assumption)
P3: 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.
Pre-think:
Data (numbers) ------>(x)------> responding to tidal distortion (conclusion)
X = data of tidal
ANS: A

4. Inference
POE:
ANS: A
B. No information
C. No information
D. Contradict. 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.
E. Contradict. 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.

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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
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C) No type of clock that keeps time more stably and
accurately than a Shortt clock relies fundamentally on
the operation of a pendulum.

?
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krodin
C) No type of clock that keeps time more stably and
accurately than a Shortt clock relies fundamentally on
the operation of a pendulum.

?

Hi Krodin - Here's my explanation - the author believes Shortt's pendulum as the ultimate one and further from the passage we find from Pierre Boucheron's experiment that the stability of the experimented pendulum was better than that of Shortts pendulum. Hence, option C is correct!! Though I got the answer wrong the first time I solved the question

Hope this helps!!
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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
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sudhirgupta93
SouthCity
Thank you all for trying. Indeed a difficult passage

The correct answer or OA is C, D, C, B

-South City

Hi! Could you please explain why C is the answer for 1st question? I'm unable to decipher it from the passage.

Hi. Even I would agree that this was a very tough passage. Still, I will try to explain.

First, we need to look at the option carefully. It says that: No type of clock that keeps time more stably and
accurately than a Shortt clock relies fundamentally on
the operation of a pendulum.

Second, note that Shortt clock used two pendulums, out of which one was only was synchronization. In the absence of this pendulum, the clock must have easily lost time and not have been more stable.

Also, it is written in the passage that the Earth variations were discovered because of the clock. If synchronization was not there in the clock ( which was achieved through the use of two pendulums, the clock would have lost time and/or the variations could not be studied. This point affirms the belief in this option.

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sudhirgupta93
SouthCity
Thank you all for trying. Indeed a difficult passage

The correct answer or OA is C, D, C, B

-South City

Hi! Could you please explain why C is the answer for 1st question? I'm unable to decipher it from the passage.

Please read the first line of the passage....The Ultimate pendulum clock, in fact best of all the mechanical clocks .
The passage also tells later that the clock is not really accurate. So combining both the statements, one can realise that the 'clock which is stable and can keep better time cannot beat the Shortt's clock since it is already the best of the pendulum clocks.
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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
It took me 10.26 minutes to solve this one....
I know its an unacceptably long. But I think seeing the length and cogent thinking required in this passage (specially in Q1 andQ3),
this passage deserves that much time.

I am sceptical about the solution of Q1, Yes the clock works on pendulum, but in the first line of the passage it is mentioned it is the best of the mechanical clocks, in the C option is too generalised saying No other clock......

Also in Q4 I was hinged between A and C, ending up choosing A. The reason being that since we in the end of 3rd para and starting of the 4th para it is mentioned about how Shott's clock is able to predict about tides. We can predict that only when we know about how the tides are caused....

Can anybody tell me where I am wrong????????????
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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
Could someone shine light on question number 2? How can it be D. IMO C is directly implied in the passage.

The only statement that I could find related to option D was the following,
Quote:
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.

and that implies it is the rotation that helped discover something about the clock and not the other way around.

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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
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Question 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.

The primary pendulum did not contain electro mechanical linkage rather ti was connected by electro mechanical linkage to secondary pendulum.

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.
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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
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niteshreddys89
Could someone shine light on question number 2? How can it be D. IMO C is directly implied in the passage.

The only statement that I could find related to option D was the following,
Quote:
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.

and that implies it is the rotation that helped discover something about the clock and not the other way around.

Hi niteshreddys89,

The answer is indeed D. The portion of the passage you have quoted talks about how the clock accounts for these movements, but the passage doesn't say that these movements were discovered as a result of the clock. Does this make sense?

Here is a quote from paragraph two:

Shortt clocks were standard provision in astronomical
observatories of the 19205 and 19305, 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.

The blue is word for word what we are looking for, per the question.

Does this help?
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Here is my interpretation of Q4.

Question 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?

Interpretation: I need to find an answer which is not directly mentioned as a detail in the passage - I need to draw an inference. The question is asking about what can be inferred about the "Chamber" in which the primary pendulum was housed.

A) It contained elaborate mechanisms that were
attached to, and moved by, the pendulum
INCORRECT: If you read the last part of the first para, it says that the secondary pendulum sent a signal to the Primary pendulum via an elaborate mechanism. From this statement, we cant figure out whether the mechanism is attached to the primary pendulum or the chamber it is housed it. Since this is an inference question, the answer MUST BE TRUE. This is a maybe ans choice. So I'd keep it on hold and come back to it if I cant find a "MUST BE TRUE CHOICE"

B) It was ﬁrmly sealed during normal operation of the
clock.
CORRECT: The passage says that the primary pendulum was kept in a vacuum chamber. This implies that it had to be air tight/ firmly sealed, else it could not be a vacuum.

C) It was at least partly transparent so as to allow for
certain types of visual data output.
INCORRECT: Maybe it was transparent, maybe it wasnt, the passage does not say anything about it.

D) It housed both the primary pendulum and another
pendulum.
INCORRECT: Nope, the passage says that the secondary pendulum was housed next to it.

E) It contained a transmitter that was activated at
irregular intervals to send a signal to the secondary
pendulum.
INCORRECT: Maybe, but if there was a transmitter, it would probably be attached to the pendulum and not the chamber it was housed in.

TAKE AWAY: At times, the gmat might give you tempting choices, such as ans choice A. Make sure you do not get confused between two objects being discussed - the pendulum and the chamber it was housed in.
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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
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9:34 mins, all correct ...need to have patience and read very diligently...make a short summary of all the paras ...then work options from wrong to right...accordting to the passage questions will be direct copy paste from para...and for inference questions, answers are always twisted so they wont be direct from paras...so go with 'wrong to right' strategy for inference questions...
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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
Hi jennpt,

Question 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

Can you please explain why A is wrong? in the exam, I was stuck between A and C. I did not pick C because I though it was too obvious. I could not find enough grounds to eliminate A. In parg 3, it says he clock was
responding to the slight tidal distortion of the earth due
to the gravitational pull of the moon and the sun.

how would they have found this out without accurate times at which
high and low ocean tides occurred? or is it because it says "various locations" when the passage did not mention anything about those locations?
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Hi oasis90

Aha - that feeling you got that C was too obvious? Ding ding ding, we have a winner.
On CR and RC inferences, I would not assume that things somehow must be more complicated. Choose the answer you can prove based on the evidence given in the passage. And if it sounds like it repeats something you already know from the passage, perfect.

And the problem with A is exactly what you suspected: "various locations." We need info about the tides, but not about the different tide times in various locations. That goes too far.
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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
Hi jennpt, can you help with the first question?

I got this in my GMAT prep test today. I was trying to find 4 incorrect options. I eliminated C because it looked too extreme. When I got to E, I realized that I had eliminated 4 options, so the answer must be E.
Any tips on how I can avoid such mistakes?
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P1: Focus words: “ultimate pendulum clock”, “ultimate mechanical clock”, “2 pendulums”, “Primary pendulum in vacuum chamber”, “secondary..electric signal”, “electromechanical linkage”.

P2: Better timekeeping, very little loss/gain of time, indicators of seasonal variations in earth’s rotation.

P3: Boucheron carried a study of Shortt Clock found in US Naval Obs. Comparision study with atomic clock of the same observatory done after replacing electromechanical linkage with optical sensing equipment. The clock responded to tidal distortion. (influencer: gravitational pull)

P4: Detail on tides on the solid body of earth, and how the value of “g” changes and period swing of pendulum affected. Loss/Gain measured.

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. ( There is definitely mention of electric signals being used but we cannot infer that none before 1921 used this)

B) Atomic clocks depend on the operation of mechanisms that were invented by William Shortt and ﬁrst used in the Shortt clock. (No detail about this from passage. Cannot infer for certain.)

C) No type of clock that keeps time more stably and accurately than a Shortt clock relies fundamentally on the operation of a pendulum. (Look at 3rd paragraph, the experimented clock which Boucheron studied was better in stability. The electromechanical linkage via which the primary pendulum ensured that the secondary never got out of step was replaced with modern optical sensing equipment. And this gave better stability.)

D) Subtle changes in the earth's rotation slightly reduce the accuracy of all clocks used in observatories after 1921. (Incorrect. Straight reject option.)

E) At least some mechanical clocks that do not have pendulums are almost identical to Shortt clocks in their mode of operation. (Nothing to back up this from the passage)

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 the solid ground as well as in oceans

D) the earth's rotation varies from one time of year to another, (CLEARLY.Note the last line of second para “The first indications of ‘seasonal variation’ of earth’s rotation....”

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. (This wasn’t of prime importance)

B) comparative data regarding the use of Shortt clocks in observatories between 1921 and 1932 (Incorrect: Experiment was done in 1984. )

C) a non-Shortt clock that was known to keep time extremely precisely and reliably (Correct : The experimental clock is being talked about. We realised the accuracy to be even better after comparing this with the observatory’s clock.)

D) an Innovative electric-power source that was not available in the 1920s and 1930s. (Flawed)

E) optical data-transmission devices to communicate between the U.S. Naval Observatory and other research facilities. (Flawed)

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. (Incorrect. What elaborate mechanism? And how far this indicates anything about the chamber in primary pendulum? Think again.)

B) It was ﬁrmly sealed during normal operation of the clock. (Correct : This can be inferred from the fact that it was kept in a vacuum chamber.)

C) It was at least partly transparent so as to allow for certain types of visual data output. (Don’t know. No information in the passage about it being transparent)

D) It housed both the primary pendulum and another pendulum. (Flawed)

E) It contained a transmitter that was activated at irregular intervals to send a signal to the secondary pendulum.

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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
Waiting to resolve the the same query as below.
niteshreddys89
Could someone shine light on question number 2? How can it be D. IMO C is directly implied in the passage.

The only statement that I could find related to option D was the following,
Quote:
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.

and that implies it is the rotation that helped discover something about the clock and not the other way around.

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Re: The ultimate pendulum clock, indeed the ultimate mechanical clock of a [#permalink]
abhinav770
Waiting to resolve the the same query as below.
niteshreddys89
Could someone shine light on question number 2? How can it be D. IMO C is directly implied in the passage.

The only statement that I could find related to option D was the following,
Quote:
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.

and that implies it is the rotation that helped discover something about the clock and not the other way around.

Hello,

This is an According to the passage question, so there shouldnt be much analysis here.

The only piece of information you need here is this The ﬁrst indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks.

Question 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 Trap to get you lost in the details

B) atomic clocks can be used in place of pendulum
clocks in observatoriesTrap to get you lost in the details

C) tides occur in solid ground as well as in oceans This is indeed stated like you pointed out. However, the trap here is that it has nothing to do with what Shortt Clocks helped in discovering. Shortt Clocks did not help to discover that tides occur in solid ground and in the oceans. It helped discover indications of seasonal variations in the earth's rotation. The passage then continues to explain how tides in ocean and solid are related to that (which we don't really need to know and its only meant to confuse us.

D) the earth's rotation varies from one time of year to another. This is what I talked about above. It's a rephrase of The ﬁrst indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks..[/color]

E) pendulums can be synchronized with one another electronically It's clear that this has nothing to do with anything
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