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Homework Help: Friction question

  1. Jul 18, 2010 #1
    A 1000kg boat is traveling at 90km/h when its engine is shut off. The magnitude of frictional force fk between boat and water is proportional to the speed v of the boar: fk=70v, where v is in meters per second and fk is in newtons. find the time required for the boat to slow to 45km/h.

    The question does not ask for acceleration, so do I need to find the acceleration before finding the time?

    In addition, Does any one knows how to use a math template for posting this type of question?

  2. jcsd
  3. Jul 18, 2010 #2
    Any thought on it would be fine, thanks.
  4. Jul 18, 2010 #3


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    Homework Helper

    Use Newton's second law to get the relation between velocity v and acceleration, dv/dt. Solve the differential equation.

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