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New to Physics - Question Help!

  1. May 2, 2010 #1
    Hey,
    I'm taking physics as a learn-at-home kinda course to get into school for electrical. I had a question about some of the logic and reason behind what the book is showing me as it doesn't explain much. The example question they gave is as follows:

    Determine the weight of a 65kg student on earth( g= 9.8m/s2 [down]).

    Given - g= 9.8m/s2 [down]
    m = 65kg

    Required - Fg=?

    Equation - Fg = mg

    Solution - Fg = (65kg)(9.8ms2)
    Fg = 637N
    Fg = 6.4 x 102N

    More or less I wanted to know why the 637N was broken up to 6.4 x 102 and how I would go about extrapolating this from every question I come across from now on.

    Any info is appreciated, I am new to physics and suck at math in general....

    p.s. the g's in the equation should have an arrow pointing to the right over them but I have no clue how to write that on this thing...

    Thanks!
     
  2. jcsd
  3. May 2, 2010 #2
    Its just a convention man..more applicable for bigger numbers...like you can write 10000000 or 10^7 they would mean the same thing...its just for the ease of writing
     
  4. May 2, 2010 #3

    Doc Al

    User Avatar

    Staff: Mentor

    They are just expressing the weight using scientific or exponential notation. (See: http://en.wikipedia.org/wiki/Scientific_notation" [Broken]) Note that they rounded off the answer to 2 significant figures instead of 3, which is more realistic since you only have the mass to 2 significant figures.


    While the acceleration is a vector, which you could express using that arrow notation, g itself is just the quantity 9.8 m/s^2.
     
    Last edited by a moderator: May 4, 2017
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