QUES: Hydrogen was liquefied for the first time by James Dewar in 1898 by using regenerative cooling and his invention, the vacuum flask. He produced solid hydrogen the next year. Deuterium was discovered in December 1931 by Harold Urey, and tritium was prepared in 1934 by Ernest Rutherford, Mark Oliphant, and Paul Harteck. Heavy water, which consists of deuterium in the place of regular hydrogen, was discovered by Urey's group in 1932. Francois Isaac de Rivaz built the first de Rivaz engine, an internal combustion engine powered by a mixture of hydrogen and oxygen in 1806. Edward Daniel Clarke invented the hydrogen gas blowpipe in 1819. The Dobereiner's lamp and limelight were invented in 1823.
What year was tritium discovered?

ANS: 1934

QUES: Two assumptions underpinned the British approach to HAA fire; first, aimed fire was the primary method and this was enabled by predicting gun data from visually tracking the target and having its height. Second, that the target would maintain a steady course, speed and height. This HAA was to engage targets up to 24,000 feet. Mechanical, as opposed to igniferous, time fuses were required because the speed of powder burning varied with height so fuse length was not a simple function of time of flight. Automated fire ensured a constant rate of fire that made it easier to predict where each shell should be individually aimed.
Another assumption was that the target would maintain a steady course along with what other two factors?

ANS: speed and height

QUES: The aircraft carrier dramatically changed naval combat in World War II, because air power was becoming a significant factor in warfare. The advent of aircraft as focal weapons was driven by the superior range, flexibility and effectiveness of carrier-launched aircraft. They had higher range and precision than naval guns, making them highly effective. The versatility of the carrier was demonstrated in November 1940 when HMS Illustrious launched a long-range strike on the Italian fleet at their base in Taranto, signalling the beginning of the effective and highly mobile aircraft strikes. This operation incapacitated three of the six battleships at a cost of two torpedo bombers. World War II in the Pacific Ocean involved clashes between aircraft carrier fleets. The 1941 Japanese surprise attack on Pearl Harbor was a clear illustration of the power projection capability afforded by a large force of modern carriers. Concentrating six carriers in a single unit turned naval history about, as no other nation had fielded anything comparable. However, the vulnerability of carriers compared to traditional battleships when forced into a gun-range encounter was quickly illustrated by the sinking of HMS Glorious by German battleships during the Norwegian campaign in 1940.
Why were carrier-launched aircraft more effective than naval guns?

ANS: They had higher range and precision

QUES: The first six presidents of the United States did not make extensive use of the veto power: George Washington only vetoed two bills, James Monroe one, and John Adams, Thomas Jefferson and John Quincy Adams none. James Madison, a firm believer in a strong executive, vetoed seven bills. None of the first six Presidents, however, used the veto to direct national policy. It was Andrew Jackson, the seventh President, who was the first to use the veto as a political weapon. During his two terms in office, he vetoed twelve billsmore than all of his predecessors combined. Furthermore, he defied the Supreme Court in enforcing the policy of ethnically cleansing Native American tribes ("Indian Removal"); he stated (perhaps apocryphally), "John Marshall has made his decision. Now let him enforce it!"
Which president vetoed six bills?

ANS:
unanswerable