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Homework Help: Newtons laws problem

  1. May 17, 2008 #1
    Joe was driving on the highway a car ahead of him was driving far below the speed limit so he decided to pass. In the first second he gained(gained means to get nearer to something you are chasing) 5m on the car and as he accelerated he gained 1.5 times as much distance in each second as he had the second before. If there was 30 m between joe and the car he was passing then how long did it take him to pass

    Correct answer

    t = 1s
    u = s/t=5/1 m/s
    a = 1.5 m/s^2

    V^2= u^2 +2as

    V^2= 5^2+ (2*1.5*2.5)
    v = sqrt100=10

    v = u + at
    10 = 5+ (1.5*t)
    t =5/1.5=3.333
    t = 3.33+1=4.33 (one second put because of first gained)

    Attached Files:

  2. jcsd
  3. May 17, 2008 #2


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    Welcome to PF!

    Hi brendanmeneze! Welcome to PF! :smile:

    I don't think this has anything to do with Newton or with constant acceleration.

    In the first second, he gains 5
    In the second second, he gains 5*1.5
    In the third second, he gains 5*1.5^2
    In the fourth second, he gains 5*1.5^3.

    Can you see a pattern? :smile:

    Anyway, after 4 seconds, he gains 5(1 + 1.5 + 2.25 + 3.375) = over 40 metres.

    Have I understood the question right? :confused:
  4. May 18, 2008 #3
    newtons laws motion

    you could right there tinytim butt the answers 5.37 s for 30m you got less seconds 4 for more meters 40m unless the answer given 537/100 is wrong. thank you and i believe you are right because laws of motion dont give right answer.
  5. May 18, 2008 #4


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    Yes, I think the answer given is wrong. :frown:

    Finish it anyway … can you see the pattern, and get an equation for the distance as a function of time? :smile:
  6. May 19, 2008 #5
    thanks tiny-tim for helping me out.
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