During the twelfth century, the Indian author Bhaskara published

Question

During the twelfth century, the Indian author Bhaskara published a drawing of a wheel with an odd number of sealed containers of mercury around its outer rim. According to the designer, as the wheel spun the cylinders of mercury would spin with it. Each time a cylinder reached the top of the wheel, gravity would pull the mercury from one side of the container to the other and exert a continuous downward force on the wheel, thus enabling it to turn perpetually without external energy. This scheme marked the first documented attempt to design a perpetual motion machine. Like the study of alchemy, the notion of perpetual motion machines has enticed inventors with the impossible for centuries; since Bhaskara’s proposal, countless designers, through either fraud or wishful thinking, claimed to have devised similar contraptions.

By definition, a perpetual motion machine is a device that can operate continuously and supply useful work with no external power source. While processes in nature such as the carbon or hydrologic cycles appear to be perpetual, they are in fact driven by the energy of the sun in the same way that a hydroelectric power plant is driven by the external power of a waterfall. Perpetual motion machines, on the other hand, are designed to harness the potential energy of gravity, buoyancy, or other physical forces in a perfectly efficient manner that essentially recycles energy.

The science that studies the behavior and rules of energy is thermodynamics. In terms of thermodynamics, there are two types of perpetual motion machines. The first is a machine that provides more energy than it requires, which violates the first law of thermodynamics: energy can neither be created nor destroyed. In the case of Bhaskara’s design, the second law of thermodynamics is violated. The second law asserts that in all energy transfers in a closed system, the potential energy after the transfer will be less than the initial potential energy, with the difference lost to dissipative forces such as drag or friction in the form of heat. Each time the mercury in Bhaskara’s wheel strikes the side of the containers, the impact generates heat, which is dissipated into the air and thus lost from the system. Because of this, 100 percent efficiency cannot be achieved and the machine will eventually come to rest.    1 
 1. The primary purpose of the passage is to:

A. illustrate erroneous designs of early scientists who did not possess a proper knowledge of the laws of physics
B. show why the overbalanced wheel cannot be made to do usable work
C. discuss the pursuit and ultimate failure of inventors to design a perpetual motion machine
D. argue that while perpetual motion cycles are possible in nature, scientists have never been able to produce a working mechanical model
E. reject a design for a perpetual motion machine and propose a working alternative

2 
 2. It can be inferred from the passage that:

A. Bhaskara rejected the validity of the laws of thermodynamics when he designed the overbalanced wheel.
B. Bhaskara’s design of the overbalanced wheel included 100 percent efficiency as one of its fundamental principles.
C. Bhaskara’s design of the overbalanced wheel constituted a scientific fraud that was not revealed until centuries had passed.
D. Bhaskara believed that the overbalanced wheel would work because he had not actually produced a working model.
E. Bhaskara designed the overbalanced wheel to demonstrate the impossibility of perpetual motion machines.

3 
 3. In paragraph two, the author discusses the carbon and hydrologic cycles in order to:

A. refute the notion that perpetual motion is only possible in technological ventures
B. illustrate how only sunlight can successfully power perpetual motion cycles
C. elaborate on the definition of perpetual motion machines through apparent examples
D. argue that hydroelectric power plants are not, in fact, perpetual motion machines
E. demonstrate that perpetual motion machines are not designed using solar energy

4 
 4. The third paragraph supplies information for answering all of the following questions EXCEPT:

A. What is the dissipative force that acts upon Bhaskara’s design of the overbalanced wheel?
B. Which law of thermodynamics is broken by Bhaskara’s design of the overbalanced wheel?
C. How does Bhaskara’s design fail to achieve totally efficient recycling of energy?
D. How might a machine violating the first law of thermodynamics be designed?
E. What is the purpose of the science of thermodynamics?

Snehaaaaa · Answer

1. The primary purpose of the passage is to:
A. illustrate erroneous designs of early scientists who did not possess a proper knowledge of the laws of physics- The passage does not states that the scientists did not posses a proper knowledge of the the laws of physics
B. show why the overbalanced wheel cannot be made to do usable work- This is not the primary purpose of the passage
 C. discuss the pursuit and ultimate failure of inventors to design a perpetual motion machine- This is the primary purpose of the passage. This is the correct answer 
D. argue that while perpetual motion cycles are possible in nature, scientists have never been able to produce a working mechanical model- This is not stated in the passage
E. reject a design for a perpetual motion machine and propose a working alternative- No alternative is stated in the passage

2. 2. It can be inferred from the passage that:
A. Bhaskara rejected the validity of the laws of thermodynamics when he designed the overbalanced wheel.- No where in the passage has Bhaskara knowingly rejected the laws of Thermodynamics. 
 B. Bhaskara’s design of the overbalanced wheel included 100 percent efficiency as one of its fundamental principles.- This is implied as per the mechanism explained for perpetual motion machine. This is the correct answer. 
C. Bhaskara’s design of the overbalanced wheel constituted a scientific fraud that was not revealed until centuries had passed.- This cannot be inferred from the passage as scientific fraud is not mentioned in passage.
D. Bhaskara believed that the overbalanced wheel would work because he had not actually produced a working model.- This is not stated in the passage
E. Bhaskara designed the overbalanced wheel to demonstrate the impossibility of perpetual motion machines.- Bhaskara had no such intention while designing the overbalanced wheel

3. In paragraph two, the author discusses the carbon and hydrologic cycles in order to:
A. refute the notion that perpetual motion is only possible in technological ventures- This is not mentioned in the passage
B. illustrate how only sunlight can successfully power perpetual motion cycles- the usage of 'only' sunlight makes this option wrong
C. elaborate on the definition of perpetual motion machines through apparent examples- This is not the author's intention
 D. argue that hydroelectric power plants are not, in fact, perpetual motion machines- This is the correct answer as the author discusses the carbon and hydrologic cycles in order to argue that they are not actually perpetual 
E. demonstrate that perpetual motion machines are not designed using solar energy- This is not the author's intention

4. The third paragraph supplies information for answering all of the following questions EXCEPT:
A. What is the dissipative force that acts upon Bhaskara’s design of the overbalanced wheel?- This is stated in the passage- frag or friction in the form of heat
B. Which law of thermodynamics is broken by Bhaskara’s design of the overbalanced wheel?- 2nd law is broken
C. How does Bhaskara’s design fail to achieve totally efficient recycling of energy?- Each time the mercury in Bhaskara’s wheel strikes the side of the containers, the impact generates heat, which is dissipated into the air and thus lost from the system.
 D. How might a machine violating the first law of thermodynamics be designed?- This is not stated in the passage. This is the correct answer. 
E. What is the purpose of the science of thermodynamics?- The science that studies the behaviour and rules of energy is thermodynamics

vrsthe1 · Answer

Reading for Comprehension: 
P1 - Perpetual motion machine ( PMM ) - what Bhaskara did -->  Intro to an invention.

P2 - Definition of PMM - seemingly no external power required, but works due to gravity, buoyancy, etc., and examples -->  Define PMM.

P3 - 2 types --type1 - violates first law of thermodynamics.
type2 - violates second law of thermodynamics -- Bhaskara's design & how. -->  shortcomings of PMM.

purpose of passage: to introduce, define and mention shortcomings of an invention.

Q1. The primary purpose of the passage is to: 
 A. illustrate erroneous designs of early scientists who did not possess a proper knowledge of the laws of physics 
 Not correct  --> only 1 design is talked about in passage and no mention of the knowledge level.

B. show why the overbalanced wheel cannot be made to do usable work 
 Not correct  --> no mention of whether the wheel can be put to work or not.

C. discuss the pursuit and ultimate failure of inventors to design a perpetual motion machine 
 Correct  --> the mention of PMM enticing inventors, but no one actually was able to make one.

D. argue that while perpetual motion cycles are possible in nature, scientists have never been able to produce a working mechanical model 
 Not Correct  --> Examples of almost possible PMM are given in para 2. but they are almost possible not a true PMM.

E. reject a design for a perpetual motion machine and propose a working alternative 
Not Correct --> did not reject or propose anything, only mentioned how PMM by Bhaskara was not possible.
--------------------------------------------------------------------------------------------------------------------

Q2. It can be inferred from the passage that:

A. Bhaskara rejected the validity of the laws of thermodynamics when he designed the overbalanced wheel. 
 Not Correct  --> we only know about what was published, nothing about the thought or science behind it was mentioned or can be inferred.

B. Bhaskara’s design of the overbalanced wheel included 100 percent efficiency as one of its fundamental principles. 
 Correct  --> without 100% efficiency the machine cannot be in perpetual motion. Hence this can be inferred from 1st paragraph, which states "enabling perpetually".

C. Bhaskara’s design of the overbalanced wheel constituted a scientific fraud that was not revealed until centuries had passed. 
 Not Correct  --> fraud was mentioned when mentioning about others who are enticed by the idea of PMM.

D. Bhaskara believed that the overbalanced wheel would work because he had not actually produced a working model. 
 Not Correct  --> we can infer that no working model was produced because nothing about experiment or model was mentioned but only the drawing. Hence without a working model inventor can believe that the PMM might work flawlessly.

E. Bhaskara designed the overbalanced wheel to demonstrate the impossibility of perpetual motion machines. 
 Not Correct  --> as it was later on from science it is understood that the PMM is not possible. Also the drawing only tells how the concept would turn perpetually without external energy but not impossibility.
---------------------------------------------------------------------------------------------------------------------

3. In paragraph two, the author discusses the carbon and hydrologic cycles in order to:

A. refute the notion that perpetual motion is only possible in technological ventures 
 Not Correct  --> no mention of the technological ventures.

B. illustrate how only sunlight can successfully power perpetual motion cycles 
 Not Correct  --> PMM cycle means no external power.. the statement itself is contradictory.

C. elaborate on the definition of perpetual motion machines through apparent examples 
 Correct  --> carbon and hydrologic cycles are mentioned as examples of how seemingly PMM are present in nature but are infact powered by sun.

D. argue that hydroelectric power plants are not, in fact, perpetual motion machines 
 Not Correct  --> there was no arguement but given as example how sun provides the external power to carbon & hydrologic cycles like water does for hydroelectric power plants.

E. demonstrate that perpetual motion machines are not designed using solar energy 
 Not Correct  --> no mention of nay PMM desinged using solar energy, but how seemily PMM process occurs in nature but use solar energy.
---------------------------------------------------------------------------------------------------------------------

4. The third paragraph supplies information for answering all of the following questions EXCEPT:

A. What is the dissipative force that acts upon Bhaskara’s design of the overbalanced wheel? 
 Not correct  --> Mentioned. impact converted to heat.

B. Which law of thermodynamics is broken by Bhaskara’s design of the overbalanced wheel? 
 Not correct  --> Mentioned. 2nd law.

C. How does Bhaskara’s design fail to achieve totally efficient recycling of energy 
 Not correct  --> Mentioned. As energy is dissipated as heat.

D. How might a machine violating the first law of thermodynamics be designed? 
 Correct  --> bhaskara's PMM violates 2nd law. hence the statement is not mentioned in the paragraph.

E. What is the purpose of the science of thermodynamics? 
 Not correct  --> Mentioned. Study the behavior and rules of energy.

Sajjad1994 · Answer

Official Explanation

1. The primary purpose of the passage is to

Difficulty Level:   650-700

Explanation

Analyze the Question Stem:

The words  "primary purpose"  signal that this is a Global question.

Make a Prediction:

Look for a choice that is in line with the Purpose.

Evaluate the Answer Choices:

(C)  matches the prediction and is correct.

(A)  is incorrect because the passage is not focused on schemes of early scientists in general, but rather on the design and failure of perpetual motion machines.

(B)  is too narrow; the failure of the overbalanced wheel is mentioned in the passage, but only in reference to the author’s larger discussion of the failure of perpetual motion machines.

(D)  is a distortion of the passage; the passage states that many natural cycles appear to be perpetual but are, in fact, driven by external power sources.

(E)  is also a distortion. The passage does reject Bhaskara’s design, but no alternative proposal for a perpetual motion machine is proposed. In fact, the author discusses at length why such designs are impossible.

Answer: C

TAKEAWAY:  In a Global question, make sure to pick an answer that encompasses the author's whole scope, not just a particular detail.

2. It can be inferred from the passage that:

Difficulty Level:   700

Explanation

Research the Relevant Text:

Because the question does not refer to a specific place in the passage, use the answer choices themselves to direct the research.

Make a Prediction:

With an open-ended Inference question, avoid predicting; the answer could come from anywhere in the passage.

Evaluate the Answer Choices:

(A)  is unsupported because the passage never states whether or not Bhaskara understood the laws of thermodynamics, let alone whether he rejected them.

(B)  is correct because the final paragraph states that the overbalanced wheel violates the second law of thermodynamics by striving for 100 percent efficiency.

(C)  is unsupported; although the end of paragraph one states that many perpetual motion machines were frauds, Bhaskara’s design is never alleged to be fraudulent.

(D)  is also unsupported; although the passage states that the overbalanced wheel appeared as a drawing rather than a working model, the passage never states whether or not Bhaskara attempted to produce such a model.

(E)  is incorrect because although the passage uses the overbalanced wheel as an example of the impossibility of perpetual motion machines, the author never states that Bhaskara intended his design to be such an example.

Answer: B

TAKEAWAY:  When you can't research because the question is open-ended, research the individual answers as needed.

3. In paragraph two, the author discusses the carbon and hydrologic cycles in order to:

Difficulty Level:   600

Explanation

Analyze the Question Stem:

The words  "in order to"  signal that this is a Logic question, which asks about the why of a specific detail.

Research the Relevant Text:

Based on context, it is clear that the author discusses these cycles in order to help explain the definition of a perpetual motion machine just given.

Evaluate the Answer Choices:

(C)  matches the prediction and is the correct answer. The discussion of the carbon and hydrologic cycles is used to give details about this definition through examples that actually aren't perpetual.

(A)'s "only"  makes it sound like the author believes perpetual motion is possible outside of technological ventures. But the author believes perpetual motion is not possible at all, and explains that the carbon and hydrologic cycles only appear to be perpetual.

(B)  contradicts the passage; the fact that the carbon and hydrologic cycles are driven by sunlight indicates that they are not perpetual motion cycles.

(D)  is incorrect because the author is not arguing anything about hydroelectric plants, and is not discussing the carbon and hydrologic cycles in order to say anything about such plants. Rather, hydroelectric plants are mentioned in the passage as another example of seemingly perpetual motion machines that are in fact driven by an external power source.

(E)  is incorrect because there is no indication from the passage that solar energy is not used as a power source in any perpetual motion machine designs.

Answer: C

TAKEAWAY:  Logic questions are quite predictable. Consider the referenced detail in context, and pause to consider how it fits in with the rest of the paragraph and passage.

4. The third paragraph supplies information for answering all of the following questions EXCEPT:

Difficulty Level:   650

Explanation

Analyze the Question Stem:

The phrase  "supplies information"  signals a Detail question. Note that this is an EXCEPT question, which means the correct answer will be the choice that contains a question not explicitly answered by paragraph three.

Research the Relevant Text:

Make a Prediction:

It is impossible to predict an EXCEPT question, as there are so many things the author did not mention or do. Instead, go to the choices, research, and eliminate those that are answered by paragraph three.

Evaluate the Answer Choices:

(A)  is answered at the end of paragraph three, and is therefore incorrect. Heat from the impact between mercury and the sealed containers is the dissipative force.

(B)  is answered in paragraph three, and is therefore incorrect. Bhaskara’s design violates the second law of thermodynamics.

(C)  is discussed throughout the paragraph. Bhaskara’s design loses energy from the heat generated by the impact between the mercury and the sealed containers.

(D)  is not answered by paragraph three, and is therefore correct. Although the first law of thermodynamics is discussed and defined, the design of a machine violating the first law is never mentioned.

Finally,  (E)  is mentioned at the beginning of paragraph three, which says thermodynamics is the study of energy.

TAKEAWAY:  Don't try to predict Detail EXCEPT questions. Instead, research and eliminate the choices that are details from the passage.

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.

During the twelfth century, the Indian author Bhaskara published

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

During the twelfth century, the Indian author Bhaskara published

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