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Homework Help: Object A catches Object B, at when?

  1. Aug 23, 2005 #1
    Hello.

    Before I state the problem, I would like to make clear that I ask for a HINT, a GUIDANCE, a DIRECTION-POINTING on the problem. What is the big picture here that I need to understand? Not necessarily requiring anyone to solve the problem for me. Thanks.



    At t = 0 and x = 0, an initially stationary blue car begin accelerate at constant rate of 2m/s^2 in positive direction of the x axis. At t = 2s, a red car traveling in an adjacent lane and in the same direction, passes x = 0 with a speed of 8 m/s and a constant acceleration of 3m/s^2; When will the red car pass the blue car?​
     
    Last edited by a moderator: Aug 24, 2005
  2. jcsd
  3. Aug 23, 2005 #2

    Danger

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    It would help if you asked a question.
     
  4. Aug 23, 2005 #3
    If not too much trouble, solve the problem step by step please.

    Otherwise, give me a hint please.
     
  5. Aug 23, 2005 #4

    Danger

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    I'm serious, bud. All that shows up in your post is the intro and a little grey box with the word 'code:' above it. I have absolutely no idea what you're referring to, let alone asking about. If that's supposed to be a link to something, it doesn't work on my system.
     
  6. Aug 23, 2005 #5
    At t = 0 and x = 0, an initially stationary blue car begin accelerate at constant rate of 2m/s^2 in positive direction of the x axis. At t = 2s, a red car traveling in an adjacent lane and in the same direction, passes x = 0 with a speed of 8 m/s and a constant acceleration of 3m/s^2; When will the red car pass the blue car?
     
  7. Aug 23, 2005 #6

    EnumaElish

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    Blue is ahead of Red but Red is accelerating more (increasing its speed at a higher rate than Blue). You need to solve for the distance x (from the origin) at which Red will catch up with Blue. Have you studied calculus? What is the definition of acceleration that you have been taught?
     
  8. Aug 24, 2005 #7

    mukundpa

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    hint: x will be the same for the two cars but for the red one the time interval is (t - 2) sec.
     
  9. Aug 24, 2005 #8

    HallsofIvy

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    Use the general formula x(t)= (1/2)at2+ v0t+ x0 to write x as a function of t for each a car. That gives you two equations in two unknowns. When one car passes the other, they will have the same position x at the same time t. Solve the two equations for x and t. t is the time one car passes the other.
     
  10. Aug 24, 2005 #9
    try out this equation --
    (1/2)*2*t*t= 8(t-2) + (1/2)*3*(t-2)*(t-2)

    also first try figuring out why this equation?
    hint -- displacement is constant..
     
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