Re: Ocean Stream Speed - To Inger.

Dylan Sung wrote:
Hello Inger,

You mentioned that knots/hour in your thread about "Ocean stream speed".
I've told you that technically, what you've written is an acceleration.

Now, after the boat has entered the stream, does the boat continue to speed
up, until it reaches it's destination, or does it reach a steady sailing
speed?

Remember, I gave a few definitions earlier.

Speed is the change of distance with respect to time.
Acceleration is the change of speed with respect to time

Let's put velocity to one side, for the moment.

Now, if a boat is travelling from the north towards the south at a constant
speed, and then hits the gulf stream, which for our purposes is travelling
west to east

(BOAT)
. |N
. |
. |
. |
. |S
.\|/
. V

-------------------->
W (Gulf Stream) E


The boat over time will do this


(BOAT)
.B North (N)
.B |
.B South (S)
.B
.B meets gulf stream here
. B
. B
. B
. B
. B -----> drag of the gulf stream current west to east
. B
. B
. B
. B boat seems to move in a south easterly direction

Assuming that the boat speed and current speed is constant the only thing
which changes is the direction of the boat which goes south easterly.


No, in addition the southward speed is reduced as the boat leaves the southward current ;-) This would also be a short period of deceleration but resulting in a markedly lower speed over ground assuming the boat is to continue sailing southwards, with a further reduction to overcome the eastward drift you show above. The speed relative to water is of course changed only minimally since the heading with respect to the wind is not changed very much.

<snip the correct description of the impulsive nature of the speed change>
.

Relevant Pages

  • Re: Ocean Stream Speed - To Inger.
    ... You mentioned that knots/hour in your thread about "Ocean stream speed". ... what you've written is an acceleration. ... Now, after the boat has entered the stream, does the boat continue to ... Let's put velocity to one side, ...
    (sci.archaeology)
  • Re: 7/18/07 Pirate Master spoilers
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  • Re: Cambridge Mays
    ... handle a boat in a non-negligible stream, ... Tideway, but very good compared to many of the crews earlier in the day, ... Chris - I'm not sure that Tideway experience would be any use at all! ... stream features largely in each June's May risk assessment? ...
    (rec.sport.rowing)
  • Ocean Stream Speed - To Inger.
    ... You mentioned that knots/hour in your thread about "Ocean stream speed". ... what you've written is an acceleration. ... Now, after the boat has entered the stream, does the boat continue to speed ... Before the boat hits the gulf stream, the boat is not moving west to east, so the component of its velocity in the east west direction is zero. ...
    (sci.archaeology)
  • Re: sliding riggers
    ... Please see Walter's very clear graphical depiction of velocities of boat, ... for the 1st 2/3 of the stroke the rower's CofG is increasing its velocity - it is accelerating. ... Moreover to produce an average mean velocity per stroke of the bow ball with respect to the finish line, any acceleration during the leg drive must compensate for any deceleration during the recovery. ...
    (rec.sport.rowing)