Results 1 to 2 of 2

Math Help - N2L/D.E easy but hard???

  1. #1
    Member i_zz_y_ill's Avatar
    Joined
    Mar 2008
    Posts
    140

    N2L/D.E easy but hard???

    A parachutist of mass 80kg falls vertically from rest from a stationary helicopter. At a distance xm blow the helicopter her velocity is vms-1. The forces acting on her are her weight and air resitance of magnitude kv^2, where k is a constant. Her terminal velocity is 70ms-1. (i) show that the motion may be modelled by the D.E

    vdv/dx = 9.8 -0.002v^2
    This makes no sense, where does the v come from. n2l staes mass x acceleration! I am missing someting vital pls help!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    10,211
    Thanks
    419
    Awards
    1
    Quote Originally Posted by i_zz_y_ill View Post
    A parachutist of mass 80kg falls vertically from rest from a stationary helicopter. At a distance xm blow the helicopter her velocity is vms-1. The forces acting on her are her weight and air resitance of magnitude kv^2, where k is a constant. Her terminal velocity is 70ms-1. (i) show that the motion may be modelled by the D.E

    vdv/dx = 9.8 -0.002v^2
    This makes no sense, where does the v come from. n2l staes mass x acceleration! I am missing someting vital pls help!
    You might find it helpful to note that
    v \frac{dv}{dx} = a
    in all cases.

    (Make sure you understand why this is so.)

    -Dan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Hard integral from easy function
    Posted in the Calculus Forum
    Replies: 3
    Last Post: January 21st 2010, 03:59 PM
  2. Easy (although hard for me) math problem
    Posted in the Algebra Forum
    Replies: 1
    Last Post: November 10th 2008, 08:58 AM
  3. An Easy-Hard Question
    Posted in the Algebra Forum
    Replies: 5
    Last Post: October 22nd 2008, 02:00 PM
  4. sequence, not easy but not hard
    Posted in the Number Theory Forum
    Replies: 5
    Last Post: December 9th 2007, 01:08 PM
  5. [SOLVED] Easy ot too Hard??
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: November 13th 2005, 06:50 PM

Search Tags


/mathhelpforum @mathhelpforum