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Homework Help: Kinematics Basics

  1. Mar 6, 2010 #1
    1. The problem statement, all variables and given/known data

    The acceleration of a particle is defined by a = -8 m/sec2. Knowing that x = 20 when t = 4 and x = 4 when v = 16, determine:

    • The time when the velocity is zero
    • The velocity and the total distance travelled when t = 11

    2. Relevant equations

    3. The attempt at a solution

    I think once I get part 'a' I can do part 'b'. Here is my attempt:

    a = -8m/sec2
    V = -8t + C.

    How can I get C? Do I need to use another representation of acceleration? I am not sure where to go.

    Any advice greatly appreciated!
  2. jcsd
  3. Mar 6, 2010 #2


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    Science Advisor
    Homework Helper

    C is the velocity at time t = 0.
    I would suggest using the formula
    s(t) = (1/2) a t² + C t + D (*)
    where C is the velocity v(0) at time t = 0 and D is the displacement s(0) at t = 0.

    If you plug in the two given points you can determine C and D. Then you can use both formula (note that v(t) = -8t + C will actually be the derivative of formula (*) above).
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