The Motor Boat

Discussion in 'Physics & Math' started by Motor Daddy, May 31, 2013.

  1. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    I'm done here. Moderation has prevailed again. (rolls eyes)
     
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  3. Pete It's not rocket surgery Moderator

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    Feel free to return when you remember the difference between upstream and downstream.
     
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  5. Aqueous Id flat Earth skeptic Valued Senior Member

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    The speed of the water current is understood to be made relative to the ground.

    No, the boat is always moving at 8 km/hr relative to the water.

    See below.

    The speed of the boat relative to the bank changes from 4.73 km/hr to 11.27 km/hr when the boat changes from driving upstream to driving downstream.

    The ground is the inertial reference frame since the water was concurrent with that frame until it departed by rolling downhill. "Upriver" is defined as any point at a higher elevation from which the water is falling to a lower elevation.
     
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  7. Steve100 O͓͍̯̬̯̙͈̟̥̳̩͒̆̿ͬ̑̀̓̿͋ͬ ̙̳ͅ ̫̪̳͔O Valued Senior Member

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    Why feed the troll? He clearly understands, otherwise he wouldn't be able to dodge so well.
     
  8. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    Boat issues

    There is a boat, an embankment, and water. I'm having some boat measuring issues and I sure would appreciate some help.

    The deal is: The boat is in water that is flowing past the embankment. The boat is maintaining a constant position along the embankment while the motor is operating at Wide Open Throttle (WOT).

    My question is: If the water is flowing past the embankment at 3.27km/hr and the boat is maintaining its position along the embankment, then how fast would the boat be going if the water was still compared to the embankment?
     
  9. Pete It's not rocket surgery Moderator

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    So, the boat is still compared to the embankment, and maintaining a speed-over-water of 3.27 km/hr.

    It would still maintain its 3.27 km/hr speed-over-water*, so now its speed past the embankment is also 3.27 km/hr.


    *This is something we could (and probably should) test with an experiment.
     
  10. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    I agree. I'll add that if the results are not EXACTLY 3.27km/hr, then....then....then there will be even MORE boat issues.
     
  11. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    Correct, the boat motor is doing work/time and the velocity of the boat is 0 m/s. No velocity, and no acceleration. The boat is at rest. The embankment is a separate object capable of its own motion, and there is no relative motion between the boat and the embankment while the boat motor is doing work/time.
     
  12. dumbest man on earth Real Eyes Realize Real Lies Valued Senior Member

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    2,856
    Motor Daddy, if I step on to a treadmill that is running at 3.27 km/h - how fast will I have to walk to maintain myself in a steady position on the treadmill ?
    Honestly, this is not all that tough of a question !
    It is not like one of those real brain teasers like; Who was buried in Grant's Tomb ? or ; What color is the Little Red Truck ?
    I freely admit to being the Dumbest Man On Earth, and you are orders of magnitude more intelligent than me, so would you please let me know what I am missing ?
    Is there something like I have to include some formula to bring Fluid Dynamics into the equation - or does the temperature of the water come into play ?
    Is my analogy of treadmill to current completely fouling the problem ?
    I would appreciate some enlightenment.
    In advance, I thank you for your time and any help you can give me to resolve my ignorance.
     
  13. exchemist Valued Senior Member

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    Hahahahaha.
     
  14. Pete It's not rocket surgery Moderator

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    Great, MD, I'm glad we agree.
    Now, try this:

    The deal is: The boat is in water that is flowing past the embankment. The boat is moving along the embankment at 4.73 km/hr while the motor is operating at Wide Open Throttle (WOT).

    My question is: If the water is flowing past the embankment at 3.27km/hr and the boat is moving along the embankment at 4.73 km/hr, then how fast would the boat be going if the water was still compared to the embankment?
     
    Last edited: Jun 13, 2013
  15. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    Did you get a more powerful motor for the boat? The other motor was WOT when the water was flowing past the embankment at 3.27km/hr, and the boat was not traveling relative to the embankment. If the boat was WOT and stationary to the embankment in 3.27km/hr water, how in the world did the boat travel 4.77 km/hr along the embankment in the same current?
     
  16. Pete It's not rocket surgery Moderator

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    10,166
    It's a different boat.
     
  17. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    Put it on the trailer, we're using my boat. The little motor on my boat will maintain a zero velocity along the embankment is 3.27km/hr current. It's not powerful enough to travel along the embankment in that direction in that current.
     
  18. dumbest man on earth Real Eyes Realize Real Lies Valued Senior Member

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    Response to post #7.
    If boat is going AGAINST the current at 4.77 km/h relative to the embankment at WOT - then still water speed should be about 8.04 km/h .
    If boat is going WITH the current at 4.77 km/h relative to the embankment at WOT - then still water speed should be about 1.5 km/h .
    Both of these answers are of course based on a current of 3.27 km/h .
     
    Last edited: Jun 13, 2013
  19. Pete It's not rocket surgery Moderator

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    I really want to know what you think happens with the more powerful boat, MD.

    It's a simple enough question, why avoid it?

    The deal is: The boat is in water that is flowing past the embankment. The boat is moving along the embankment at 4.73 km/hr (note slight change from previous post) while the motor is operating at Wide Open Throttle (WOT).

    My question is: If the water is flowing past the embankment at 3.27km/hr and the boat is moving along the embankment at 4.73 km/hr, then how fast would the boat be going if the water was still compared to the embankment?
     
  20. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    Pete, If you want to discuss my boat, great. I'm not interested in discussing your boat. The deal was.....The boat is in water that is flowing past the embankment. The boat is maintaining a constant position along the embankment while the motor is operating at Wide Open Throttle (WOT).
     
  21. Pete It's not rocket surgery Moderator

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    10,166
    We've answered that scenario, MD. Do you have any other questions about it?

    If not, then why can't you answer my question? Is it too difficult?
    It seems to me that you're obstructing discussion.
     
  22. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    5,105
    We didn't even discuss it. You simply asserted that my boat would travel a speed of 3.27km/hr in still water, and then you came up with your own scenario.
     
  23. dumbest man on earth Real Eyes Realize Real Lies Valued Senior Member

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    Sorry - I did not know this was private conversation.
    I thought this was a forum.
    Thought I was allowed to ADD my "Two Cents" - but literally all I did was SUBTRACT .04 km/h.
     
    Last edited: Jun 13, 2013

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