QUES: A few lines of the Paris Métro in France operate on a four-rail power scheme because they run on rubber tyres which run on a pair of narrow roadways made of steel and, in some places, concrete. Since the tyres do not conduct the return current, the two guide rails provided outside the running 'roadways' double up as conductor rails, so at least electrically it is a four-rail scheme. One of the guide rails is bonded to the return conventional running rails situated inside the roadway so a single polarity supply is required. The trains are designed to operate from either polarity of supply, because some lines use reversing loops at one end, causing the train to be reversed during every complete journey. The loop was originally provided to save the original steam locomotives having to 'run around' the rest of the train saving much time. Today, the driver does not have to change ends at termini provided with such a loop, but the time saving is not so significant as it takes almost as long to drive round the loop as it does to change ends. Many of the original loops have been lost as lines were extended.
Why were many of the original loops kept?

ANS: unanswerable

QUES: After the war, Feynman declined an offer from the Institute for Advanced Study in Princeton, New Jersey, despite the presence there of such distinguished faculty members as Albert Einstein, Kurt Gödel and John von Neumann. Feynman followed Hans Bethe, instead, to Cornell University, where Feynman taught theoretical physics from 1945 to 1950. During a temporary depression following the destruction of Hiroshima by the bomb produced by the Manhattan Project, he focused on complex physics problems, not for utility, but for self-satisfaction. One of these was analyzing the physics of a twirling, nutating dish as it is moving through the air. His work during this period, which used equations of rotation to express various spinning speeds, proved important to his Nobel Prize–winning work, yet because he felt burned out and had turned his attention to less immediately practical problems, he was surprised by the offers of professorships from other renowned universities.
Where did Feynman turn down a job after the war?

ANS: unanswerable

QUES: One of the Han's greatest mathematical advancements was the world's first use of negative numbers. Negative numbers first appeared in the Nine Chapters on the Mathematical Art as black counting rods, where positive numbers were represented by red counting rods. Negative numbers are used in the Bakhshali manuscript of ancient India, but its exact date of compilation is unknown. Negative numbers were also used by the Greek mathematician Diophantus in about 275 AD, but were not widely accepted in Europe until the 16th century AD.
How were negative numbers first described during the Han period?

ANS: as black counting rods

QUES: In 1888, the Italian administration launched its first development projects in the new colony. The Eritrean Railway was completed to Saati in 1888, and reached Asmara in the highlands in 1911. The Asmara–Massawa Cableway was the longest line in the world during its time, but was later dismantled by the British in World War II. Besides major infrastructural projects, the colonial authorities invested significantly in the agricultural sector. It also oversaw the provision of urban amenities in Asmara and Massawa, and employed many Eritreans in public service, particularly in the police and public works departments. Thousands of Eritreans were concurrently enlisted in the army, serving during the Italo-Turkish War in Libya as well as the First and second Italo-Abyssinian Wars.
In what year was the Asmara-Massawa Cableway completed?

ANS:
unanswerable