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Thread: Another SUVAT Question

  1. #1
    Junior Member Mist's Avatar
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    Another SUVAT Question

    A particle Pis moving on the x-axis with constant decleration 4ms-2. At time t=0, P passes through the origin O with velocity 14ms-1 in the positive direction. The point A lies on the axis and OA=22.5. Find a) the differance between the times when P passes through A, b)The total distance travelled by P during the intervals between the lines.

    I was able to answer the first half of the question but I got stuck in the middle of it. I reached till 0=-4t^2+28t-50. I used the quadratic formula but I got the wrong answer and I can't figure a way to factorise it.

    Any help?
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  2. #2
    Senior Member
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    Quote Originally Posted by Mist View Post
    A particle Pis moving on the x-axis with constant decleration 4ms-2. At time t=0, P passes through the origin O with velocity 14ms-1 in the positive direction. The point A lies on the axis and OA=22.5. Find a) the differance between the times when P passes through A, b)The total distance travelled by P during the intervals between the lines.

    I was able to answer the first half of the question but I got stuck in the middle of it. I reached till 0=-4t^2+28t-50. I used the quadratic formula but I got the wrong answer and I can't figure a way to factorise it.

    Any help?
    a) using $\displaystyle s=ut+0.5at^2$

    $\displaystyle x=14t-0.5(4)t^2$

    $\displaystyle solve.$

    $\displaystyle t=9/2 or 5/2$

    $\displaystyle
    difference = 9/2 - 5/2 = 2s
    $

    b) using$\displaystyle v=u+at
    $

    $\displaystyle v=-4t+14$

    $\displaystyle -14=-4t (v=0)$

    $\displaystyle t=3.5s$

    sub into the equation.

    $\displaystyle x=14t-0.5(4)t^2$

    $\displaystyle x=14(3.5)-0.5(4)(3.5)^2$

    $\displaystyle x=24.5*2
    =49m$

    For this question, im assuming the distance from O->A then A->O.

    Hope this helps!
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