找回密码
 欢迎注册
查看: 5761|回复: 2

[分享] 陶哲轩的数学题

[复制链接]
发表于 2011-12-20 19:03:07 | 显示全部楼层 |阅读模式

马上注册,结交更多好友,享用更多功能,让你轻松玩转社区。

您需要 登录 才可以下载或查看,没有账号?欢迎注册

×
Suppose you are trying to get from one end A of a terminal to the other end B. (For simplicity, assume the terminal is a one-dimensional line segment.) Some portions of the terminal have moving walkways (in both directions); other portions do not. Your walking speed is a constant v, but while on a walkway, it is boosted by the speed u of the walkway for a net speed of v+u. (Obviously, given a choice, one would only take those walkways that are going in the direction one wishes to travel in.) Your objective is to get from A to B in the shortest time possible.
在机场中,你想从A点前往B点。(为了将问题简化,假设机场是一条线性通道。)一些区域有电动扶梯(双向的),另一些区域没有。你的步行速度恒定为v,电动扶梯的运行速度为u,因此在扶梯上,你的实际速度为v+u。(显然,你不会搭乘与你前进方向不一致的扶梯。)你的目标是尽可能快地从A点到达B点。
1. Suppose you need to pause for some period of time, say to tie your shoe. Is it more efficient to do so while on a walkway, or off the walkway? Assume the period of time required is the same in both cases.
1. 假定你需要暂停片刻,比如系鞋带。请问你应该在电动扶梯上系,还是在没有上电动扶梯时系?假定两种情况下,系鞋带的时间相同。
2. Suppose you have a limited amount of energy available to run and increase your speed to a higher quantity v' (or v'+u, if you are on a walkway). Is it more efficient to run while on a walkway, or off the walkway? Assume that the energy expenditure is the same in both cases.
2. 假定你有有限数量的多余能量,用来奔跑。在跑动时,你的速度提高到v'(如果在电动扶梯上,就相应为v'+u)。请问你应该在电动扶梯上跑,还是在没有上电动扶梯时跑?假定两种情况下,你可供奔跑的能量相同。
3. Do the answers to the above questions change if one takes into account the various effects of special relativity? (This is of course an academic question rather than a practical one. But presumably it should be the time in the airport frame that one wants to minimise, not time in one’s personal frame.)
3. 在狭义相对论的情况下,上述答案是否发生改变?
毋因群疑而阻独见  毋任己意而废人言
毋私小惠而伤大体  毋借公论以快私情
发表于 2011-12-20 20:27:34 | 显示全部楼层
毋因群疑而阻独见  毋任己意而废人言
毋私小惠而伤大体  毋借公论以快私情
您需要登录后才可以回帖 登录 | 欢迎注册

本版积分规则

小黑屋|手机版|数学研发网 ( 苏ICP备07505100号 )

GMT+8, 2024-3-29 19:09 , Processed in 0.042218 second(s), 17 queries .

Powered by Discuz! X3.5

© 2001-2024 Discuz! Team.

快速回复 返回顶部 返回列表