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 · Answer

Hi  Will2020

For a detail question in RC, you need to be able to  put your finger (pretty much literally) on one or more sentences in the passage that PROVE your answer . As you know, extreme language in answer choices makes them  suspicious  - it raises the bar of how strong the proof must be to support the answer. Your correct inference answer choice must NEVER be based on speculation  ("well, it COULD be true, maybe sorta") . If you are speculating, you are not approaching the question effectively.

So on to the answer choices you mentioned:
A - Yes, "no one" is extreme. But what kills this answer choice is what it's about - using electricity to aid in timekeeping functions, and when was the first time that a clock did that. Do we have any idea about the history of this? Absolutely not. The passage isn't talking about this; the focus is more on the accuracy of these Shortt clocks as best-in-class for mechanical clocks. 
D - Indeed, "all clocks" is the killer here. Atomic clocks are held up in this passage as seemingly the most accurate clocks, and we have no information about whether changes in the earth's rotation affect them.
E - How could this possibly make sense? The Shortt clock relies on this special setup with the two pendulums that the passage spends a bunch of time telling us about. So how could other clocks with no pendulums be "almost identical" in their mode of operation? It's pretty counter-intuitive, so the author would have needed to dedicate some time to explaining this. Of course, the author did not touch this topic at all (modes of operation that don't use pendulums but are still similar) so this answer is out of scope.

My advice to you is to get much deeper into the passage when you read and tackle the questions. It's like a courtroom trial and you need to be clear about the evidence that is presented to you: what it says, and what it doesn't say. If you just kind of skim through the passage casually, you are not preparing yourself to be effective on these 700-level questions.

Does this help? Let me know.

Best, Jenn

BrightOutlookJenn · Answer

Hi  Will2020

The key word is "discovery".  A discovery is a big deal and something that should register with you upon reading the passage ... even if you don't remember exactly what they found, you'll likely remember that they found  something , and you'll have an idea of  where to go back in the passage  to look for the exact thing they found. 
The two discoveries are announced at the end of the second paragraph and the end of the third paragraph (with more details about that second discovery in the fourth paragraph). The first discovery was using the clocks to learn something new about the Earth, and the second discovery was using the difference between atomic clock time and Shortt clock time to learn something new about Shortt clocks. Once you get clear on these two things, you might narrow down the answer choices to C and D.

However, D is the one we can prove, using the last sentence in the second paragraph  "The ﬁrst indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks."  as evidence.

KarishmaB · Answer

Will2020 
Yes, (A) and (D) are wrong because of the use of "no one" and "all" but not because these words indicate strong language. It is because these words are not supported by the passage. Note that the answer (C) uses similar "strong language" - no type of clock. 
But it is supported by the passage:
"The ultimate pendulum clock, indeed the ultimate mechanical clock of any kind, was invented by a British engineer, William Shortt."
As for (E), the passage gives us nothing about "mechanical clocks that do not have pendulums".

KarishmaB · Answer

I agree that question 1 was tricky but question 2 was not. I read the passage, read question 1, felt a little lost and had to read the passage again. After the second read though, question 1 was obvious since nothing else was supported by the passage at all. Also, answer to question 2 was right there.

"The ﬁrst indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks."
This told me that Shortt clocks told us about seasonal variations.

So question 2 .. led to the discovery that ... 
just reminded me that shortt clocks told us about seasonal variations. One run of the answers and it was obviously (D).

When the questions are not specific data questions and more "which of the following is implied?" or "what would the author agree with?" variety, it might be a good idea to read the passage carefully - twice. Even if you spend 4-5 mins doing that, your answers would stare right at you.

Vegita · Answer

Hey  VeritasKarishma

In questions number 2, option E says, "pendulums can be synchronized with one another electronically" and this looks quite persuading as well. How did you eliminate this option?

KarishmaB · Answer

Vegita  - Note that the passage doesn't say that synchronised pendulums were not used before in any other instrument. So we don't know whether the Shortt clock was the first one to do it. 
Also, we need identify a "discovery" that was made with the "use" of Shortt clock. So what was it that existed before but had not been discovered till Shortt clocks started getting used?

The passage tells us:
"The ﬁrst indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks."

So there are seasonal variations in earth's rotation and these were discovered by the use of Shortt clocks - makes sense.

mSKR · Answer

Thanks  VeritasKarishma  ma'm for making this tough para looks so easy. I found that the answers are staring directly. I was looking at wrong place before and trying to make sense out of nothing.

Please give a suggestion
Sometimes specific lines could not be located in the passage when try to solve question. 
Example: While solving Q2
2. According to the passage, the use of Shortt clocks led to the discovery that
I looked in 1st para and 2nd para where any information about shortt clocks was present. 
I shortlisted A, B and D in my first reading

The went to . 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.  to reject A.
went to " 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.  " to reject C
Then arrive at the text after hunting in the passage. Finally extracted the meaning.

While reading, many times I don't extract specific information. Hence while solving questions, in which we need to find out which option is true , if could not locate the right sentence for specific information then tends to get it wrong.
My Query:
How to improve efficiency of such questions and get to the right text instead of fishing the key words in the passage.
What can be done while reading the passage that we come back to the right content.

Please suggest . VeritasKarishma   GMATNinja

KarishmaB · Answer

Try to read the passage not because you have to but because you want to. For example, if it were a recent press release related to your profession, you would want to read it to find out what has happened, how it impacts you, your work etc. 
When you read a passage, think what the author is saying to you. Imagine someone saying those statements to you and try to understand them. When we glaze over passages with a closed mind, we read without actually comprehending much. It's not a "mark the keywords" exercise. It is reading comprehension so the questions will try to find whether you understood what the author was saying. 
Practice this and over time you will see a difference.

prachiyadav · Answer

Hello,

Can someone please help with this question:

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?

GMATNinja · Answer

Question 4

The chamber for the primary pendulum is discussed in the first paragraph:

"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."

From this, we know that the primary pendulum's chamber:
  was vacuum sealed 
 was close to the cabinet for the secondary pendulum 
 allowed electrical signals to be passed between the two pendulums

So, which of the following is most strongly suggested by this information? 
 
We know that there was an "elaborate electromechanical linkage" that allowed the primary pendulum to control the secondary pendulum. However, we don't know  exactly  what this linkage looked like -- was it actually  attached to and moved by  the primary pendulum? Or did it merely sense the movement of the primary pendulum? There's not enough information to say. If anything, because we know that the primary pendulum "swung freely" it seems unlikely that there were mechanisms physically attached to the pendulum.

(A) is out.

The primary pendulum was kept in a vacuum chamber. To maintain a vacuum, the chamber must have been quite firmly sealed.

(B) is strongly suggested by the information in the passage, so keep (B).

We know that  electrical  signals passed between the two pendulums, but we don't know if any  visual  data was passed from the chamber.

Eliminate (C).

Nope, the secondary pendulum was housed in a " neighboring  cabinet," not in the same chamber.

Get rid of (D).

We know that the secondary pendulum sent signals to the primary pendulum at  regular  intervals -- once every 30 seconds. Then, the primary pendulum ensured that the secondary one never got out of step by using an "an elaborate electromechanical linkage."

If anything, this system implies that the primary pendulum was in contact with the secondary pendulum at  regular  intervals. We certainly can't infer that it sent signals to the secondary pendulum at "irregular" intervals.

(E) is out, and (B) is the correct answer to question 4.

I hope that helps!

Mavisdu1017 · Answer

hello expert,
any expert can help on Q2? I know it should be pinpointed "The ???rst indications of seasonal variations in the earth's rotation were gleaned (by the use of) Shortt clocks", but I can't understand what "seasonal variations" has something to do with "earth's rotation varies"? Hope you explain, and thanks.

RonTargetTestPrep · Answer

"The earth's rotation" isn't derived from any other phrase in the text. That exact phrase occurs BOTH in the text AND in the answer!

The text says that Shortt clocks enabled researchers to detect
  seasonal variations in   the earth's rotation

The answer choice:
  the earth's rotation   varies from one time of year to another

The color-coded pieces go together. "Varies" and "variation" are forms of the same word, so you only have to recognize that  seasons  are  times of year .

Vatsal7794 · Answer

Hi Experts

GMATNinja   KarishmaB   MartyTargetTestPrep

Can somone please explain question 1. I am not able to understand that how we are inferring answer from first line of te passage
According to me the answer is D (Also Can you please give reason why option D is wrong)

KarishmaB · Answer

1. The passage most strongly suggests that its author would agree with which of the following statements about clocks?

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

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

It tells us that Shortt clock is the "ultimate" pendulum clock - the best pendulum clock. So no clock that is better than a Shortt clock uses a pendulum. If there were, then Shortt clock would not be the "ultimate" pendulum clock.

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

From the passage: 
 The ﬁrst indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks.

Shortt clocks told us about the seasonal variations in the Earth's rotation. We measured time accurately using these clocks and hence came to know that there are seasonal variations in the earth's rotation.
Seasonal variations have no impact of the clock.

Answer (C)

KarishmaB · Answer

Question 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.

In 1921, the first ultimate pendulum clock was installed in an Observatory. It doesn't mean that no one had designed a clock that used electricity before that. In fact, since it was the "ultimate", likely some basic versions were designed much before 1921.

B) Atomic clocks depend on the operation of mechanisms that were invented by William Shortt and first used in the Shortt clock.

Not suggested anywhere.

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

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

It tells us that Shortt clock is the "ultimate" pendulum clock - the best pendulum clock. So no clock that is better than a Shortt clock uses a pendulum. If there were, then Shortt clock would not be the "ultimate" pendulum clock.

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

The passage doesn't mention any impact of seasonal variations on atomic clocks so "all clocks" is certainly incorrect. Ignore.

E) At least some mechanical clocks that do not have pendulums are almost identical to Shortt clocks in their mode of operation.

No such information available. The passage does not discuss any mechanical clocks that do not have pendulums.

Answer (C)

Question 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

Given: The first indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks.
By using Shortt clocks, we first found that there are seasonal variations in the earth's rotation. Hence (D) is correct.

Option (C) is not correct because we are given that the clock responded to the slight tidal distortion of the earth due to the gravitational pull of the moon and the sun, but the clock did not help us discover tides occuring in solid ground.

Answer (D)

Question 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

The study described is this: In 1984 Pierre Boucheron carried out a study of a Shortt clock... 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.

This study would not have been possible without the atomic clock - a clock we know to be extremely precise. Without a precise scale of measurement, we would not have been able to calculate the error in Shortt clock.

Answer (C)

Question 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.

What do we know about the Shortt clock's primary pendulum?

Given: 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.

We are given that "via an elaborate electromechanical linkage, the primary pendulum ensured that the secondary pendulum never got out of step." but which chamber had this elaborate electromechanical linkage we do not know. The primary pendulum was in a vacuum chamber while the secondary pendulum was housed in a neighboring cabinet so the linkages could have been in either.

B) It was firmly sealed during normal operation of the clock.

Correct. We are given that it is a vacuum chamber. So it had ot be firmly sealed.

C) It was at least partly transparent so as to allow for certain types of visual data output.

Transparency of the chamber is not discussed.

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

It housed only the primary pendulum. The secondary pendulum was in a cabinet.

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

We know that the secondary pendulum activated it at regular intervals, not irregular. Hence incorrect. I don't even want to check whether a transmitter is mentioned or not.

Answer (B)

RenB · Answer

KarishmaB   AjiteshArun   HarshR9 , can you please help me out with the first one? 
I chose D. My reasoning was- I dont know if these subtle changes are affecting  'all clocks'  after 1921. - Is this thought correct or I could have inferred that atomic clocks are not affected by tides/ rotation? 
Reason for rejecting C- I dont know if there are any other pendulum clock which works on the pendulum mechanism and is better than the Shortt clock.

But now that I think, the first line says that Shortt clock was the  'ultimate'  pendulum clock- no other pendulum clock was better than the Shortt clock. So any clock that was better than the Shortt clock was defs not a pendulum clock - Is this reasoning correct?

Also, when the qs asks- ' most strongly suggests'  that its author would agree- Can I say that the inference doesnt ' have to'  be true? There could always be a small possibility that the inference is not true? I am asking this so that in case an option like C arises, I can say to myself, there is a teeny possibility that this ay not be true, other options feel more wrong than this one, I know the reasons why, so go for it. Is this thought okay?

AjiteshArun · Answer

Hi RenB,

1. Yes, we don't know if these changes affect all clocks. The passage tells us "the cycle of the tides caused  the clock  to gain or lose up to 140 microseconds". This part is about the Shortt clock in the basement of the USNO ("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").

2. Again, yes. The passage calls the Shortt clock the  ultimate  pendulum/mechanical clock, which means that there is no better pendulum clock, no better mechanical clock.

3. Yes. Must be true questions are relatively rare, and we're more likely to see regular inference (in both CR and RC). And it's generally a good idea in verbal to check the other options as well.

HarshavardhanR · Answer

Hi RenB,

On choice C  - sounds a bit twisted, but it cannot be rejected. Your thinking is in the right direction imo. (Yes).

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

- The author calls the ultimate pendulum clock (the Shortt clock) "the  ultimate   mechanical clock  of any kind". This means that as per the author, there is no better mechanical clock. In other words, the Shortt clock is the absolute best of all mechanical-type clocks. Thus, the Shortt clock is also better than any other clock that also relies on pendulum operation (because those would also be mechanical locks, obviously). 
- The author also clearly praises this clock on "stability" and "accuracy". In fact, the author's christening of this clock as the ultimate one seems to be in these contexts. 
- Thus, overall, the passage does seem to suggest that no other pendulum-based clock is as stable and accurate as the Shortt clock. Keep C on hold.

On choice D - you are correct (yes). "all clocks" was the major red flag for me.

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

All we know if that the Shortt clock was useful in figuring out the subtle differences in the earth's rotation based on season (para 2, actually!). Perhaps this means that the Shorrt clock was able to maintain accuracy even when earth's rotation changed slightly. Great. We have no idea about other clocks. We can infer nothing about "all clocks" post 1921. The issue is the same even if we talk about the other phenomenon (tidal distortion).

Most strongly suggests  -> yes, we are not searching for a "must be true" answer. We are looking for a choice that has reasonable (not necessarily definite) basis, from the passage. The other choices will be ideas with no tangible support/basis.

___
Harsha
Passionate about all things GMAT | Exploring the GMAT space | My website: gmatanchor.com

VerbalBot · Answer

Automated notice from GMAT Club VerbalBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

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

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Reading Comprehension (RC) Questions

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

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards