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Please help fast. Projectory object!

  1. Feb 3, 2009 #1
    1. The problem statement, all variables and given/known data

    Ink droplets in an ink-jet printer are ejected horizontally at 12 and travel a horizontal distance of 1.0 to the paper.

    How far do they fall in this interval?

    2. Relevant equations
    ?


    3. The attempt at a solution

    so v0 = 12 m/s

    x = 1 mm.

    ??I am not geting the question
     
  2. jcsd
  3. Feb 3, 2009 #2
    umm...i think you use
    x = (v0) (t) and solve for time

    then use the time for one of the kinematics equation as if it were free fall? does that make sense to you?
     
  4. Feb 3, 2009 #3
    can you explain what they mean by " How far do they fall in this interval? "
     
  5. Feb 3, 2009 #4
    i think basically its just asking for the height the ink dropped from the pen onto the paper
     
  6. Feb 3, 2009 #5
    so would this be correct :

    x = v0 *t.

    t = x/v0

    = 1mm / 12 m/s

    = 0.001m / 12 m/s

    t = 8.3 x 10^-5

    so using the equation,

    Y = Y0 +Vy0*t -1/2 g*t^2

    y = 0 + 12(8.3 x 10^-5) - 1/2 (9.8) (8.3 x 10 ^-5)^2

    = 10.0 x 10^-4
     
  7. Feb 3, 2009 #6
    I see no problem with the time. The equation you used was correct too but the problem is that vyo = 0 m/s and not twelve because the angle of elevation from the horizontal is 0 therefore vyo = sin (0 degrees) (12 m/s) = 0 m/s
     
  8. Feb 3, 2009 #7
    Are you sure because vy0 ( read as initial velocity of y) ? which i think should be 12
     
  9. Feb 3, 2009 #8
    well vy0 is the initial velocity in the y-direction. In other words the vertical direction. The ink was ejected horizontally 12 m/s so thats why the vy0 = 0 m/s
     
  10. Feb 3, 2009 #9
    x = v0 *t.

    t = x/v0

    = 1mm / 12 m/s

    = 0.001m / 12 m/s

    t = 8.3 x 10^-5

    so using the equation,

    Y = Y0 +Vy0*t -1/2 g*t^2

    y = 0 + 0(8.3 x 10^-5) - 1/2 (9.8) (8.3 x 10 ^-5)^2

    = -3.40 x 10^-8....

    The number should not be negative?
     
  11. Feb 3, 2009 #10
    Its negative because of the frame of reference. remember displacement is a vector? its only negative because its downward. the opposite would be true
    the distance is just 3.40 x 10^-8
     
  12. Feb 3, 2009 #11
    so should the answer be the absolute value of the answer.
     
  13. Feb 3, 2009 #12
    yes I believe so
     
  14. Feb 3, 2009 #13
    Thank you for you help. As you can see I am very new to this and also having a hard time grasping the method and concept of solving physics problem. Although I do not know why, because I am relatively good at quantitative work.
     
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