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.