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Ultimate pendulum Clock - William Shortt

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Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 30 Jul 2016, 22:07
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Question 1
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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 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.

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.


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


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


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.

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

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New post 31 Jul 2016, 11:24
2
My reasoning for the answers:

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.

Please comment. Thanks.
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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 02 Aug 2016, 05:55
any help in decoding this passage and the questions ??
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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 13 Aug 2016, 09:27
1
Could somebody explain please why answer to Q1 is
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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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 14 Aug 2016, 20:45
Can anyone explain why question 4 is B?
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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 14 Aug 2016, 23:48
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2
krodin wrote:
Could somebody explain please why answer to Q1 is
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: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 15 Aug 2016, 04:54
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davidm21 wrote:
Can anyone explain why question 4 is B?


Please note the passage has "The primary pendulum swung freely in a vacuum chamber"

Here the answer (B) defines the word vacuum.


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

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New post 23 Aug 2016, 07:20
Tough Passage. :(

My answers were ACAA but it seems OA answers are all different.

Can someone please help decoding this passage?
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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 28 Aug 2016, 02:11
Keats wrote:
This is such a horrible passage mostly having inference questions :| I wonder who can get all right in first go.


But what if this passage is their on the actual GMAT. What to do in that case? :(
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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 29 Aug 2016, 12:00
As per my understanding, the word 'vacuum' in the first passage suggests that the chamber was firmly sealed during normal operation of the clock.
Hence, answer B for the question number 4.
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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 10 Sep 2016, 02:51
gandhigauravz wrote:
As per my understanding, the word 'vacuum' in the first passage suggests that the chamber was firmly sealed during normal operation of the clock.
Hence, the answer is B for question number 4.


This question was the only one I got wrong. B was a runner up, but I am still not convinced, since the correct answer implies that one should know that vacuum can be achieved in a firmly sealed chamber.
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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 12 Sep 2016, 06:24
SouthCity wrote:
Thank you all for trying. Indeed a difficult passage

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

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Hi! Could you please explain why C is the answer for 1st question? I'm unable to decipher it from the passage.
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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 03 Oct 2016, 06:55
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sudhirgupta93 wrote:
SouthCity wrote:
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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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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New post 13 Nov 2016, 09:34
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sudhirgupta93 wrote:
SouthCity wrote:
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: 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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Re: Ultimate pendulum Clock - William Shortt  [#permalink]

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

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

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

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New post 04 Nov 2017, 00:59
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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: Ultimate pendulum Clock - William Shortt   [#permalink] 04 Nov 2017, 00:59

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