It returns in 7 hours upstream the river.
The speed of river stream is 2mph.
The speed of the wind is 4mph.
What is the angle between the wind and the river?
2007-09-05 04:22:37 · 3 answers · asked by Alexander 6 in Science & Mathematics ➔ Physics
In the rest frame of the water the boat travels 21 - 2*3 = 15 miles downstream and 21 + 2 * 14 = 35 miles upstream, so its speed with respect to the water is 5 mph in both directions. In order for these two speeds to be *exactly* the same, the angle between the wind and the course must also be the same, which is to say the wind must come in at a 90 degree angle. This is in the frame of the river so that means the wind is blowing (toward) 60 degrees away from the downstream direction. The key to solving these problems of Alexander is Faith (that an incontrovertible answer exists).
The boat speed is substantially more than the wind speed - that may be possible - I don't know much about sailing.
2007-09-05 12:20:15 · answer #1 · answered by shimrod 4 · 2⤊ 0⤋
As I already told you yesterday: if you don't provide a function that relate the angle of the wind, relative to the boat, to the speed of the boat over the speed of the wind we cannot give a meaningful answer.
2007-09-05 11:44:44 · answer #2 · answered by paulatz2 2 · 0⤊ 0⤋
Alexander, more info is needed. Is the sail on a fixed boom or a movable one? Are you allowing unlimiteds time for the turn around or not? Let's be more definite in the parameters...
2007-09-05 11:38:18 · answer #3 · answered by ponyboy 81 5 · 0⤊ 0⤋