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Kinematic question Pls help

  1. Apr 6, 2015 #1
    1. The problem statement, all variables and given/known data
    A girl shoves a book at rest on a table and it moves with an acceleration of 1.3 m/s . After 5 s, the book falls at the edge of the table. If the table height is 1.2 m, find the horizontal distance that it hit the floor. (ans: 3.22 m) ... How the answer would be 3.22

    2. Relevant equations

    3. The attempt at a solution

    Actually in this question doesn't have the angle .. So is it right to choose the maximum height formula so I can have the angle and then apply the Horizonte distance which is v0^2 sin2(q)/g
  2. jcsd
  3. Apr 6, 2015 #2


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    I would break the problem into two parts, horizontal and vertical motion.

    You know the height and the initial vertical velocity. How long in seconds does it take to hit the ground?

    Calculate the horizontal velocity. How far does it travel horizontally in the same time?
  4. Apr 6, 2015 #3


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    The angle is simply zero cause the velocity of the book, just before it starts falling, is horizontal.
  5. Apr 6, 2015 #4

    Which formula for both parts ?
  6. Apr 6, 2015 #5
    Yeah ..I just solve it thank so much
    First we find the velocity from this formula v=at
    Then we apply to find the time that it take to hit the ground which from this formula y=y0+v0y(t)+(1/2)gt^2
    Finally we just multiply between the velocity from the answer 1 (6.5) and time 0.16

    Is it right ??
  7. Apr 6, 2015 #6


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    well yes and no. The time it takes from the moment it passes the edge of table to the moment it hits the ground isnt 0.16 according to my calculations. Just use h=(1/2)gt2
  8. Apr 6, 2015 #7
    Ooh so the time will be 0.49 s

  9. Apr 6, 2015 #8


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    yes but still you have to understand something, when you wrote the equation for y, [itex]y=y_0+v_{0y}t+(1/2)gt^2[/itex] it is [itex]v_{0y}=0[/itex] cause the book starts its fall with only horizontal velocity component.
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