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HW Help

  1. Sep 16, 2006 #1
    A boat floats across this river, and back,
    It takes 5 hours for it to reach point B, from point A, and then 7 hours to
    return to point to point A from point B.

    Naturally it's because not because the crew got tired on the way back,
    but because the flow of the river, or it's angle which is pretty much more of the same.

    the question is: How much time will it take for a log to arrive from point A, to point B?.

    I believe the V0=Constant(The flow), otherwise that teacher would have said mentioned it.

    i believe the equation is:

    The equation with all the numbers intact should look like that:


    and there is another equation i can add, based upon the fact that the distances AB, and BA are the same.



    does anyone have a clue how can i sole this correctly?, because my solution just doesn't seems correct at all.


    or is it:
    Last edited: Sep 16, 2006
  2. jcsd
  3. Sep 16, 2006 #2


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    Welcome to the Forums,

    Let me see if I've got this question straight in my head. A boat starts from point A to B, this takes five hours. Then the boat turns around and floats back to point A under no propulsion. You need to know how long it will take a log to float from A to B?

    Have I got that about right? Is there a diagram?
  4. Sep 16, 2006 #3

    It floats 7 hours back, with propulsion, apparently against the flow, or the angle of the river, or any constant force for that matter.

    i need to calculate how quickly will a block of wood arrive from point A, to point B, driven by the flow of the river obviously, so what i need to find is V0, which is the speed of the river flow
  5. Sep 16, 2006 #4


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    Do you have the velocity of the boat? Width of the river? I diagram would be very useful here. I am assuming that point A is downstream from point B.
  6. Sep 16, 2006 #5
    It's the other way around, point B, is a downstream from point A.

    I don't have the Velocity of the boat, Just the info i provided.

    I'm suppose to find V1 and V0 with an equation, it isn't supposed to be a problem since we are dealing with constant speeds here
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