[maths] Re: position function; calculus

  • From: "Ned Granic" <ngranic@xxxxxxx>
  • To: <maths@xxxxxxxxxxxxx>
  • Date: Thu, 7 Dec 2006 04:54:15 -0700

Already Nelson! Thanks a lot. What I've got then is:
s(t) =-cos t-sin t+6t+1.
Correct?
----- Original Message ----- 
  From: Nelson Blachman 
  To: maths@xxxxxxxxxxxxx 
  Sent: Thursday, December 07, 2006 1:48 AM
  Subject: [maths] Re: position function; calculus


  Ned,

    Your integrations are correct, but your substitutions of the values at time 
t=0 are wrong.

    While sin 0 = 0, cos 0 is not 0.

    HTH
    --Nelson
    ----- Original Message ----- 
    From: Ned Granic 
    To: maths@xxxxxxxxxxxxx 
    Sent: Tuesday, December 05, 2006 10:45 AM
    Subject: [maths] position function; calculus


    Hi all,

    Here is one little confusing question that needs some clarification.

    A particle is moving with the given data.
    Find the position of the particle.

    a(t) = cos t + sin t -- acceleration
    s(0) = 0 -- position at 0 seconds
    v(0) = 5 -- initial velocity.
    a(t) = v^'(t)  -- acceleration is a derivative of a velocity
    = cos t + sin t, that is, velocity is antiderivative of the acceleration, 
therefore, the velocity function is:
    v(t) = sin t-cos t+C
    which means that:
    5 = 0+C, that is:
    C = 5, and the required velocity function is:
    v(t) = sin t-cos t+5.
    Then, the velocity function is a derivative of the position function:
    v(t) = s^'(t), that is, the position function is antiderivative of the 
velocity function:
    s(t) = -cos t-sin t+5t+D, that is:
    0 = 0+D, or:
    D = 0, so the required position function here is:
    s(t) = -cos t-sin t+5t.

    The question is, what is the position of the particle with the given data?

    Many thanks in advance!
    Ned

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