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The fog (Posted on 2005-11-01) Difficulty: 3 of 5
Somewhere on the high seas smuggler Stan is attempting, without much luck, to outspeed coast guard Charlie, whose boat can go faster than Stan's. Charlie is one mile east of Stan when a heavy fog descends. It's so heavy that nobody can see or hear anything further than a few feet. Immediately after the fog descends, Stan changes course and attempts to escape at constant speed under a new, fixed course. Meanwhile, Charlie has lost track of Stan. But Charlie happens to know Stan's speed, that it is constant, and that Stan is sticking to some fixed heading, unknown to Charlie.

How does Charlie catch Stan?

Charlie may change course and speed at will. He knows his own speed and course at all times. There is no wind, Charlie does not have radio or radar, there is enough space for maneuvering, etc.

  Submitted by Hugo    
Rating: 2.6667 (3 votes)
Solution: (Hide)
One way Charlie can catch Stan is as follows.

Charlie waits until he knows that Stan has traveled for one mile. At that time, both Stan and Charlie are somewhere on a circle with radius one mile, and with its center at the original position of Stan. Charlie then begins to travel with a velocity that has a radially outward component equal to that of Stan, and with a tangential component as large as possible, given Charlie's own limitation of total speed. By doing so, Charlie and Stan will always both be on an identical circle having its center at the original position of Stan. Because Charlie has a tangential component whereas Stan does not, Charlie will always catch Stan.
Please also read Bob Smith's comment here.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re(4): new twistMindy Rodriguez2005-11-07 22:04:19
re(3): another twistMindy Rodriguez2005-11-07 21:59:39
SolutionClearing away the fog: solution and admissionMindy Rodriguez2005-11-06 01:59:58
re: Possible SolutionMindy Rodriguez2005-11-04 20:25:55
A hole in the fogMindy Rodriguez2005-11-04 20:20:28
Some ThoughtsPossible Solutiondopey9152005-11-04 18:50:38
Some Thoughtsre(4): new twistMindy Rodriguez2005-11-03 22:39:37
re(2): another twistJoe2005-11-03 16:26:57
re(3): new twistBob Smith2005-11-03 08:35:53
Questionre(2): new twistMindy Rodriguez2005-11-02 23:07:59
re: another twistMindy Rodriguez2005-11-02 23:05:26
another twistJoe2005-11-02 17:54:51
re: new twistBob Smith2005-11-02 12:08:17
re: JutlandgoFish2005-11-02 03:06:45
re(2): No SubjectPenny2005-11-02 03:02:35
re: No SubjectDustin2005-11-02 00:16:03
possible solutionjeffrey2005-11-01 23:10:16
Some Thoughtsnew twistMindy Rodriguez2005-11-01 22:50:10
No SubjectPenny2005-11-01 21:43:57
Consider the followingJen2005-11-01 19:58:02
Wouldn't Charlie just...Joe2005-11-01 19:06:38
Game PlaygoFish2005-11-01 14:56:35
guessSean2005-11-01 13:09:09
SolutionahoyJosh706792005-11-01 12:34:59
Some Thoughtsre: solutionSatan2005-11-01 11:02:58
SolutionsolutionSatan2005-11-01 10:58:33
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