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Ultimate pendulum Clock - William Shortt

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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 25 Nov 2016, 19:42
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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New post 31 Aug 2017, 07:49
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.

Thanks in advance!
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New post 17 Sep 2017, 09:13
really good passage.

3/4 in 8.3min.
'
But for question 4 why is the ans. b r8? (yet it has 1 indication that 'primary pendulum swung freely in a vacuum chamber.')
Why is the ans. c not r8. (visual information is badly needed to take data ' 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.')
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New post 18 Sep 2017, 10:17
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: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 02 Nov 2017, 07:59
niteshreddys89 wrote:
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.

Thanks in advance!


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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New post 04 Nov 2017, 00:59
3
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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New post 21 Nov 2017, 05:04
any elaborate explanation anyone?
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New post 05 Dec 2017, 11:10
Time Taken 10+ Minutes

Got 2/4 correct.
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New post 05 Jan 2018, 14:39
Easy passage - tough questions.
12mins EDCA
2/4
got tricked in ques 4
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New post 06 Jan 2018, 02:15
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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New post 13 Feb 2018, 11:49
Can anybody explain why answer C in Q2 is wrong?
"In addition to causing the familiar ocean tides, both the sun and the moon raise tides in the solid body of the earth."

C) tides occur in solid ground as well as in oceans

Thanks
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New post 21 Feb 2018, 04:30
:( Difficult passage
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New post 23 Feb 2018, 08:18
2
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
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New post 03 Jun 2018, 13:26
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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New post 05 Jun 2018, 11:13
2
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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New post 05 Jun 2018, 14:05
jennpt wrote:
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.


Understood. Many thanks and Kudos :)
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New post 20 Jul 2018, 07:29
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. :sad:
Any tips on how I can avoid such mistakes?
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New post 21 Jul 2018, 05:17
2
Hi sandman13

#1 is a pretty tough inference question. But we get our evidence for C from the very first sentence:

Quote:
The ultimate pendulum clock, indeed the ultimate mechanical clock of any kind, was invented by a British engineer, William Shortt.


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
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Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 21 Jul 2018, 21:54
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: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 22 Jul 2018, 22:24
I don't understand. Can you please elaborate which question you want an explanation to?
naveenraja1994 wrote:
answers to this question??

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Re: Ultimate pendulum Clock - William Shortt &nbs [#permalink] 22 Jul 2018, 22:24

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