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SIN练习题第4题答案解析

SIN练习题第4题

4.The ice storm this winter in the province of Quebec strained many wires to the breaking point. In a particular situation, the transmission pylons are separated by 500 m of wire. The top grounding wire is 15° from the horizontal at the pylons, as in the diagram, and has a diameter of 1.5 cm. The steel wire has a density of 7860 kg/m3. When ice (density 900 kg/m3) built up on the wire to a total diameter of 10.0 cm, the wire snapped. What was the breaking stress (force/unit area) in N/m2 in the wire at the breaking point?
You may assume the ice has no strength.

(A) 7.4 X 107 (B) 4.4 X 108 (C) 2.6 X 106 (D) 1.15 X 107 (E) 6.7 X 108

SIN练习题4答案及解析

答案：（B）   解析如下

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SIN练习题第5题答案解析

SIN练习题第5题

5.Romeo is landing back on Earth to claim his bride, Juliet. His spaceship is descending vertically at 50 m/s and he is 500m up when he throws a bouquet of Lovelon flowers horizontally (from his point of view) out of his ship to land near Juliet, who is waiting at the dockport, 40 m from his landing spot. How fast must Romeo throw his flowers in m/s so that they land at Juliet's feet? (Lovelon flowers are very slippery, and do not experience air resistance. They can also absorb quite a shock on landing and still look fresh!).

(A) 1.96 (B) 2.52 (C) 4.00 (D) 5.24 (E) 6.44

SIN练习题5答案及解析

答案：E；解析如下

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SIN练习题第6题答案解析

SIN练习题第6题

6.A teenager is downloading pirated, compressed songs in MP3 format from the Internet. Each song is about 3 minutes long when played, and needs about 2.9 megabytes of computer storage. To fill a CD requires about 70 minutes of music. If a 56K modem is being used which gives on average about 30 kilobits/sec of data flow, how many minutes does it take to download a full CD's worth of songs, ignoring setup times and filename entries? A byte represents 8 bits.

(A) 301 (B) 203 (C) 187 (D) 38 (E) 14

SIN练习题第6题答案解析

答案：A；解析如下：

With each song being 3 minutes long, there are 23.33 songs on a 70-minute CD. This requires a total storage of 2.9 megabytes x 23.33 = 67.67 megabytes. The modem processes about 30 kilobits/sec, which is 3.75 kilobytes/sec. At this rate, 67.67 megabytes will take (67.67x106)/(3750) = 18045 seconds or 301 minutes (A) or 5.01 hours!

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