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Force=MA question

  1. Mar 13, 2014 #1
    1. The problem statement, all variables and given/known data
    A boat moves through the water with two forces acting upon it. One is [F1x]=20000N forward push by the water on the propeller, and the other is [Ffrx]=2000n resistivive (friction) force due to the water around the bow
    (A) What is the acceleration of the boat?
    (B) If it starts from rest,how far will the boat move in 10s?
    (C) what will the velocity be in the end of that time?
    (D) what is the boat weight?

    2. Relevant equations

    3. The attempt at a solution I know that the netforce will be 18000N but I really don't know where to go from there. I know the F=ma but without extra information I don't know what to do. Please help
  2. jcsd
  3. Mar 13, 2014 #2
    Is it even possible to solve with just this information?
  4. Mar 13, 2014 #3

    Andrew Mason

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    Homework Helper

    Where did you get this problem? Are you asked to solve in terms of the mass of the boat?

  5. Mar 13, 2014 #4
    I got this from my professor as part of my homework. No I am not asked to solve in terms of mass, it is exactly as I typed it.
  6. Mar 14, 2014 #5


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    Staff: Mentor

    Hi smartjack. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    You need additional information to solve this, e.g., the boat's mass.

    Besides, it is an unrealistic situation, to say the boat experiences a constant friction force. Fluid friction varies steeply with speed.
    Last edited by a moderator: May 6, 2017
  7. Mar 14, 2014 #6


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    Dearly Missed

    IF OP has given ALL information, this is indeed, stangely worded and insoluble. (That's why I highly doubt it is true)

    IF, however, somewhere else, OP has been given a pseudoformula for the resistive force within which the mass of the boat is an included parameter, THEN the problem might be technically solvable.

    (But, I would probably take issue with such a formula, but that's beside the main point here)
  8. Mar 14, 2014 #7
    I talked to the professor, and he said he must have left out the mass of the boat. Which with the mass I can easily solve the problem. Thank you for your help, I tried to work on this for hours and was getting no where, I thought I had missed something fundamental in my classes.
  9. Mar 14, 2014 #8


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    Staff: Mentor

    Thanks for getting back. :smile:
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