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Homework Help: Lots of problems with UNITS

  1. Jun 1, 2014 #1
    Hello, I am having lots of problems with units. I don't know why but I am getting sick of it. I don't know what am I doing wrong.

    Let me give you an example.

    I have this problem:
    A football player kicks a 0.41-kg football initially at rest; and the ball flies through the air. If the kicker's foot was in contact with the ball for 0.51 s and the ball's initial speed after the collision is 21 m/s, what was the magnitude of the average force on the football?

    My attempt:

    F = mv/t
    F = (0.41 kg) (21m/s) / 0.051s
    F = (8.61 Kg. m. / s) / 0.051 s
    F = (8.61 kg.m) / 0.051 s^2
    F = 169 kg.m/s^2

    why is my unit so wrong??? (kg.m/s^2) (my answer should be in NEWTONS)
  2. jcsd
  3. Jun 1, 2014 #2
    Those units of yours are the same as Newtons.

  4. Jun 1, 2014 #3
    of course :redface:

    i think I need a break

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