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

Question

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.   1 
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.
 C 
 2 
 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
 D 
 3 
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
 C 
 4 
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.
 B

BrightOutlookJenn · Accepted Answer

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

saurabh3 · Answer

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

smartyman · Answer

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.

brockr1 · Answer

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.

?

notYet · Answer

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!!

mymygmat2016 · Answer

Question 1:

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.

Dabu3790 · Answer

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.

oasis90 · Answer

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?

BrightOutlookJenn · Answer

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.

sandman13 · Answer

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?

Smiti25 · Answer

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.

Thank you, and have a great day ahead.
Happy Learning!

amitanshumaity · Answer

Dabu3790  Don't you think firmly sealed = vacuum chamber is far fetched assumption?

For the inference to be  must be true  the assumption has to be  must be true

Manukaran · Answer

Hi  GMATNinja , for Q1, would D have been correct if instead of:

Subtle changes in the earth's rotation slightly reduce the accuracy of all clocks used in observatories after 1921.

It would have been:

Subtle changes in the earth's rotation slightly reduce the accuracy of all  mechanical  clocks used in observatories after 1921.

KrishnakumarKA1 · Answer

Hello...

Let me try to help you with the first 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.

Let us talk about Options C and D.

C - This option would have been extreme if the phrase "than a Shortt Clock" was not present. If that was the case, then it would have talked about all the clocks. However, the phrase "than a Shortt Clock" links it to the passage.

D - The addition of the word "mechanical" to Option D would not make any difference. It still talks about all mechanical clocks - The passage doesn't give information on this.

Hope that resolves the doubt.

All the best,

Thanks,

Saikiran Dudyala
Byju's GMAT Verbal Expert.

GMATNinja · Answer

Manukaran , there is not enough information in the passage to prove whether or not your modified answer choice is correct. The first sentence of the passage indicates that the Shortt clock is a pendulum clock, which is  one kind  of mechanical clock. Your modified answer choice would apply to  all  mechanical clocks used in observatories after 1921, and the passage simply does not provide information about those other clocks.

In general, changing the wording of an answer choice is not likely to help you much on RC. In a perfect world, you want to build the habit of addressing each answer choice in its exact, original language; playing with hypothetical answer choices isn't the best use of your valuable study time.

I hope this helps!

amitanshumaity · Answer

Question 4 is still not clear. Can someone please help with a detailed explanation on this.

VeritasKarishma   egmat   generis

KarishmaB · Answer

It is the other way around.

vacuum chamber => firmly sealed.

The passage tells us that the primary pendulum was housed in a vacuum chamber. It certainly implies that the chamber was firmly sealed (else you cannot maintain vacuum).
So option (B) must be true.

Will2020 · Answer

Hi BrightOutlookJenn GMATNinja VeritasKarishma ! How can we eliminate the wrong answer choices? I did notice the strong language in A - "no one" - and D - "all clocks" - are they wrong because of it? What about E? Many tks!

Will2020 · Answer

Hi BrightOutlookJenn GMATNinja VeritasKarishma ! Question 2 was tough because it lacked a key word to search for. So, I ended up spending a lot of time in this question. What was your thought process to solve the question? I had to go trough each AC, using process of elimination to finally pick the right answer, but doing so was very time consuming and I couldn't prove the right AC during the test. Tks!

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

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

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