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Homework Help: 1D Kinematics

  1. Jul 6, 2010 #1
    1. The problem statement, all variables and given/known data
    A speeding car traveling at 20m/s passes a stationary police car, which immediately begins to accelerate at 2.0 m/s. The speeder travels with uniform motion until the police car is along side. How long does it take the police car to catch up to the speeder.

    v1: 20m/s

    Police Car:
    v1: 0 m/s
    a: 2.0 m/s^2

    2. Relevant equations

    d=v1*t + 0.5*a*(t^2)

    3. The attempt at a solution
    If figure the displacement between the cars should be 0 when they meet so
    Ds = displacement of speeder
    Dp = displacement of police

    Ds + Dp = 0

    (20)t + 0.5(2.0)t = 0

    Thats my attempt its a pretty sorry one but I really need help.
  2. jcsd
  3. Jul 6, 2010 #2
    I think you may have meant t^2..

    Anyways you are basically stating above that the car and the police will have traveled the same distance in the same amount of time. So you can write one equation for the for the amount of time the car is moving and equation for the amount of time the police is moving and set them equal to each other and solve for d..
    Or you could write two equations for the distance each move, set them equal to each other, solve for t, and then plug t back in either equation and get d.
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