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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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B
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Question Stats:

36% (01:41) correct 64% (02:09) wrong based on 387

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Question 2
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57% (00:29) correct 43% (00:21) wrong based on 378

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Question 3
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60% (00:31) correct 40% (00:35) wrong based on 354

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Question 4
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52% (01:06) correct 48% (01:35) wrong based on 355

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GMAT PREP Exam Pack 2 - Exam 6 Question - OA after 3 Responses
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.

-South City


Question 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.

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

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

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

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.

[Reveal] Spoiler: Question #1 OA
[Reveal] Spoiler: Question #2 OA
[Reveal] Spoiler: Question #3 OA
[Reveal] Spoiler: Question #4 OA

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

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New post 31 Jul 2016, 06:48
answers to this question??

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

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New post 31 Jul 2016, 11:24
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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 31 Jul 2016, 22:14
I believe

ACAA

Please do provide OA

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

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New post 31 Jul 2016, 22:54
My answers : CCAB

SouthCity Please include OA while posting the questions.

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

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New post 01 Aug 2016, 06:37
winionhi wrote:
My answers : CCAB

SouthCity Please include OA while posting the questions.


winionhi please see my comment above. I am looking for 3 answers before posting OA. you will be surprised.

Last edited by SouthCity on 01 Aug 2016, 06:40, edited 1 time in total.

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

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New post 01 Aug 2016, 06:39
Thank you all for trying. Indeed a difficult passage

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

-South City

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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
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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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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
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.


-South City

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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, 02:07
This is such a horrible passage mostly having inference questions :| I wonder who can get all right in first go.

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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

-South City


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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Ultimate pendulum Clock - William Shortt [#permalink]

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New post 03 Oct 2016, 06:55
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] 13 Nov 2016, 09:34

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