Shooting down an ice-covered track, a bobsled（大雪橇）can go faster than 80 miles an hour, and riders can feel force five times stronger than the pull of gravity. A race can be won or lost by one hundredth of a second. How do bobsleds go faster than cars on a highway? The answer is a combination of athletics and science.
At the start of a race, the crew push their sled, building up speed before they jump in for the ride. For months before the race, the crew have built up power in their legs. The push is the crew's only chance to add speed. All other work goes into keeping friction and drag（摩擦力和阻力）from slowing the sled down.
The design of the sled's runners（滑板）reduces their friction with the ice. The friction of a moving runner melts a little ice right under the runner, and the runner rides on that thin layer of water. The runners are rounded on the bottom. Runners that are too flat may not melt enough ice for fast ride. Runners that are too round may become too warm, softening the ice and slowing the sled down. No amount of rounding is perfect for all races because the hardness of the ice depends on the weather on race day.
Bobsleds used to be open. The riders did not sit inside a hull（外壳）. As the crew sped down the track，the air would create drag. Today, a sled's hull reduces drag by splitting the air in front of the sled and making it flow smoothly along the slides. As with the runners，strict rules apply to the hull. For example，no team may add any part that would create helpful air currents.
Reducing friction and drag creates another challenge: high speeds. “The faster the sleds car travel on the run, the more thrilling the race,” one research team wrote. “But the track must not be too fast: he crew still need to be able to reach the bottom safely.”
1. What's the text mainly about?| A．The shape of the sled. | B．The design of the runners. |
| C．The safety rules applying to the sled. | D．The elements relating to the sled's speed |
| A．Proper amount of melted ice is needed for a fast ride. |
| B．The rounder the runners are, the faster the sled goes. |
| C．Thin layer of water would drag the runners backward. |
| D．A sled's movement has nothing to do with weather. |
| A．It's comfortable to sit in. | B．It leads to beneficial air flow. |
| C．It helps to create a safe ride. | D．It's free from strict rules. |
| A．Safety is the most important. | B．Keeping high speed is difficult. |
| C．Riders' desire to win is understandable. | D．The crew's cooperation is necessary. |
2 . The conductor on the podium (指挥台) has no baton (指挥棒), no tailcoat and no musical score, but Android Alter 3 is kicking up a storm as it guides a symphony orchestra's players through their paces.
The robot has a humanoid face, hands and lower arms, which gesture with what could pass for passion as it bounces up and down and rotates during the live performance of Keiichiro Shibuya's opera Scary Beauty in the Emirate of Sharjah.
Video from the recent performance in the Emirate of Sharjah showed the machine turning to face orchestra members and waving its arms. Alter 3 even sang at times.
Shibuya said the involvement of robots in the everyday lives of humans is continually increasing. But, he said he thinks people will need to decide in the future how artificial intelligence can best improve the human experience.
Shibuya added that he believes humans and robots can learn to work together to create beautiful art. "This work is a metaphor of that relations between humans and technology," he said. Shibuya noted that sometimes the music-leading robot can "get crazy", making it difficult for the musicians to keep up. But other times, the humans and machines cooperate very well.
Shibuya said the robots and AI that exist today are "far from complete". He is interested in studying how such incomplete technology can be combined with art.
"I think this is a very exciting idea…We came to see what it looks like and how much is possible," said Anna Kovacevic. Another audience member, who gave his name only as Billum, said after the show, "You know, a human conductor is so much better." Although he said he is interested in AI and looks forward to big developments, he concluded on the project: "The human touch is lost."
1. What does Shibuya think of Alter 3?| A．It is not perfect at present. | B．It teams up with humans well. |
| C．It often makes humans crazy. | D．It is better than human conductors. |
| A．The performance drew mixed reactions. |
| B．Billum took no interest in the performance. |
| C．The audience were fascinated by the performance. |
| D．The audience thought Alter 3 would have a bright future. |
| A．Positive | B．Negative. | C．Objective. | D．Critical. |
| A．Robot Cooperates with Humans |
| B．Robot Conducts Human Orchestra |
| C．The Significance of Robots in Art |
| D．The Relations Between AI and Humans |
