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9yr old 7th grader needs help!

  1. Sep 18, 2008 #1
    I have a problem in my science book,we think the teachers edition may have a mistake? Can someone look at my problem and explain how to find the answer? I am home schooled, and like mom said, 7th grade was too many years ago!

    Calculate mass: You push yourself on a skateboard with a force of 30N and accelerate at 0.5 m/s squared. Find the mass of the skateboard if your mass is 58kg.

    We keep coming up with a different answer than the book. Can someone explain this so we can make sure we are doing it correctly?

    Thank You!

    << personal e-mail address edited out by berkeman >>

    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    Last edited by a moderator: Sep 18, 2008
  2. jcsd
  3. Sep 18, 2008 #2


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    The equation is force = mass * acclearation or F=ma
    Since we know f and a and want m we have to re-arrange the formula this gives m=f/a
    If you plug in the numbers you get m = 30N/0.5ms-2 = 60kg
    Since you have a mass of 58.5kg the mass of the skateboard is the difference.
  4. Sep 25, 2008 #3
    you divide 30n by 0.5 m/s and you will get ur anwser which you then subtaract 58 from and you will get ur anwser it will have this unit of measure kg*m/s N
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