|Part 1|

You should spend about 20 minutes on Questions 1-12, which are based on the Reading Passage 1.

Jupiter's Comet Collision

[In 1994 the comet Shoemaker-Levy 9 collided with the planet Jupiter, causing great excitement in the world of astronomy. The article which follows was written after the first impact.]

Shoemaker-Levy 9 has plunged into Jupiter, and the Hubble Space Telescope has moved away to look at other objects in space. Amateur astronomers, however, are still watching Jupiter see what bruises were left on the mighty planet by the comet crash of 1994. There was tremendous excitement in astronomical circles during the collision of comet and planet. It is now time to see what has been learned from this impact.

One question which may never be answered: Was Shoemaker-Levy 9 a comet, or was it an asteroid instead? Comets tend to be a mixture of ice, rock, and dust, along with other substances, like carbon monoxide, that evaporate quickly to form a halo and a tail. Scientists studying the chemical composition of the spots on Jupiter where Shoemaker-Levy 9 (S-L 9) hit thought they might see evidence of water and oxygen, two of the expected products when an icy comet vaporizes. But except for one unconfirmed report, researchers have found only ammonia, hydrogen sulfide, and sulfur gas.

Asteroids are rockier than comets. Yet an asteroid can have a halo or a tail, made mostly of dust. Says Hal Weaver of the Space Telescope Institute: "The only real evidence that SL-9 was a comet is that it broke apart, and we've never seen that in an asteroid. But maybe this was a fragile asteroid".

Amateur astronomer David Levy, who with Eugene and Carolyn Shoemaker discovered SL-9, points out that comets were originally distinguished by their appearance. They are objects that look like fuzzy stars with tails, and in any previous century, astronomers would have called this discovery a comet. On that basis, argues Levy, "S-L 9 is a comet, period."

The apparent absence of water at the impact sites provides a clue about how far the SL-9 fragments penetrated Jupiter's atmosphere before exploding. Theorists think that a layer of water vapor lies some 95 km below the visible cloud tops; above the vapor layer, about 50 km down, are clouds believed to consist of a sulfur compound. Since no water seems to have been stirred up, the explosion probably took place in the presumed sulfide layer.

If researchers confirm that the sulfur rose from Jupiter, it will be a major discovery,' says University of Arizona astronomer Roger Yelle. We've always believed that much of the color in Jupiter's clouds comes from sulfur compounds, but we've never detected them.

No one knows why the points of impact are so dark, but it is clear that they are very high up in Jupiter's atmosphere, since the planet's stripes can be seen through them. Astronomers believe the collisions will provide an opportunity to study the winds above Jupiter's cloud tops. The mark left by the first impact is already starting to be spread around. There are also hints of seismic waves ripples that may have traveled to a dense layer of liquid hydrogen thousands of kilometers down and then bounced back up to the surface, creating rings half the size of the planet's visible face. These waves may offer clues to Jupiter's internal structure.

The spots that were made by the collision will undoubtedly blow away eventually, but it's much too soon to tell if there will be any permanent changes in Jupiter. There is still every chance that the impacts, especially from the four fragments that hit in nearly the same place, will destabilize the atmosphere and create a new, permanent cyclone like Jupiter's Great Red Spot.

It's also possible that the show isn't quite over. Theorists using a computer model argue that debris has lagged behind the original 21 major fragments. These stragglers, they predict, will keep hitting Jupiter for months to come. Unlike the previous fragments, the latecomer will smash into the near side of the planet, giving astronomers a chance to watch some strikes directly. Is the theory plausible? Says one astronomer, 'We've had so many surprises from S-L 9 already that I wouldn't rule anything out.'

|Part 2|

You should spend about 20 minutes on Questions 13-26, which are based on the Reading Passage 2.

Fashion and Society: A Historical Perspective

|Part 3|

You should spend about 20 minutes on Questions 27-42, which are based on the Reading Passage 3.

Mass Production

Car manufacturer Henry Ford s 1908 Model T automobile was his twentieth design over a five-year period that began with the production of the original Model A in 1903. With his Model T, Ford finally achieved two objectives. He had a car that was designed for manufacture, and one that was easily operated and maintained by the owner. These two achievements laid the groundwork for the revolutionary change in direction for the entire motor vehicle industry.

The key to mass production wasn’t the moving, or continuous, assembly line. Rather, it was the complete and consistent interchangeability of parts and the simplicity of attaching them to each other. These were the manufacturing innovations that made the assembly line possible. To achieve interchangeability, Ford insisted that the same gauging system be used for every part all the way through the entire manufacturing process. Previously, each part had been made to a slightly different gauge, so skilled fitters had to file each part individually to fit onto the other parts of the car. Ford’s insistence on working to gauge throughout was driven by his realisation of the payoff he would get in the form of savings on assembly costs. Ford also benefited from recent advances in machine tools able to work on pre-hardened metals. The warping or distortion that occurred as machined parts were being hardened had been the bane of previous attempts to standardise parts. Once the warping problem was solved, Ford was able to develop innovative designs that reduced the number of parts needed and made these parts easy to attach. For example, Ford’s four-cylinder engine block consisted of a single, complex casting. Competitors cast each cylinder separately and bolted the four together.

Taken together, interchangeability, simplicity, and ease of attachment gave Ford tremendous advantages over his competition.

Ford’s first efforts to assemble his cars, beginning in 1903, involved setting up assembly stands on which a whole car was built, often by one fitter. In 1908, on the eve of the introduction of the Model T, a Ford assembler’s average task cycle, that is the amount of time he worked before repeating the same operations, totalled 514 minutes, or 8.56 hours. Each worker would assemble a large part of a car before moving on to the next. For example, a worker might put all the mechanical parts, such as wheels, springs, motor, transmission and generator, on the chassis (body), a set of activities that took a whole day to complete. The assembler/fitters performed the same set of activities over and over at their stationary assembly stands. They had to get the necessary parts, file them down so they would fit (Ford hadn’t yet achieved perfect interchangeability of parts), then bolt them in place.

The first step Ford took to make this process more efficient was to deliver the parts to each workstation. Now the assemblers could remain at the same spot all day. Later in 1908, when Ford finally achieved perfect part interchangeability, he decided that the assembler would perform only a single task and move from vehicle to vehicle around the assembly hall. By August of 1913, just before the moving assembly line was introduced, the task cycle for the average Ford assembler had been reduced from 514 to 2.3 minutes. Naturally, this reduction spurred a remarkable increase in productivity, partly because complete familiarity with a single task meant the worker could perform it faster, but also because all filing and adjusting of parts had by now been eliminated. Workers simply popped on parts that fitted every time.

Ford soon recognised the problem with moving the worker from assembly stand to assembly stand: walking, even if only for a yard or two, took time, and jam-ups frequently resulted as faster workers overtook the slower workers in front of them. Ford’s stroke of genius in the spring of 1913, at his new Highland Park plant in Detroit, was the introduction of the moving assembly line, which brought the car past the stationary worker. This innovation cut cycle time from 2.3 minutes to 1.19 minutes; the difference lay in the time saved in the worker’s standing still rather than walking and in the faster work pace which the moving line could enforce. The moving assembly sped up production so dramatically that the savings Ford could realise from reducing the inventory of parts waiting to be assembled far exceeded this trivial outlay.

Even more striking, Ford’s discovery simultaneously reduced the amount of human effort needed to assemble an automobile. What’s more, the more vehicles Ford produced, the more the cost per vehicle fell. Even when it was introduced in 1908, Ford’s Model T, with its fully interchangeable parts, cost less than its rivals. By the time Ford reached peak production volume of 2 million identical vehicles a year in the early 1920s, he had cut the real cost to the consumer by an additional two-thirds.

To appeal to his target market of average consumers, Ford had also designed unprecedented ease of operation and maintainability into his car. He assumed that his buyer would be a farmer with a modest tool kit and the kinds of mechanical skills needed for fixing farm machinery. So the Model T’s owner’s manual explained in 64 pages how the owner could use simple tools to solve any of the 140 problems likely to occur with the car.

Ford’s competitors were as amazed by this designed-in repairability as by the moving assembly line. This combination of competitive advantages catapulted Ford to the head of the world’s motor industry and virtually eliminated craft-production companies unable to match its manufacturing economies. Henry Ford’s mass production drove the auto industry for more than half a century and was eventually adopted in almost every industrial activity in North America and Europe.