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Homework Help: Only twi forces

  1. Nov 23, 2008 #1
    Only two foces act on a 3.0 kg mass.?
    Only two foces act on a 3.0 kg mass. One of the forces is 9.0 N east, and the other is 8.0 N in the direction of 62.0 north of wet. What i the magnitude of the acceleration of the mass? The mass has only TWO forces acting on it. No gravity. Not resting on any other surface

    Fx=ma

    9cos0-8cos62=3a
    a=1.7m/^2

    i that rigth
     
  2. jcsd
  3. Nov 24, 2008 #2

    PhanthomJay

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    That's the acceleration in the east or positive x direction. You need also to calculate the acceleration in the northerly or positive y direction, then find the magnitude of the acceleration using Pythagorus' Theorem.
     
  4. Nov 24, 2008 #3
    Fx=ma
    9cos0-8cos62=3a
    a=1.7m/^2
    Fy=ma
    9sin0-8sin62=ma
    ay= 1.97
    a=(1.2^2 + 1.97^2)^1/2 a=2.30 m/s^2 is it right now and thanks for your help
     
  5. Nov 24, 2008 #4

    PhanthomJay

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    Well, your math is not very good. 9cos0 = 9, and 8cos62 = 3.75. ax = 1.75m/sec^2.

    9sin0 is 0, and 8sin62 is 7.06. ay = -7.06m/sec^2. Now solve for a.
     
  6. Nov 24, 2008 #5
    a=((1.75^2) +(-7.06^2))^1/2 =7.28m/s^2

    how about it now
     
  7. Nov 24, 2008 #6
    but you forget to divide the Fy by Mass that -7.06/3 to get the ay that is -2.35

    --------------------------------------------------------------------------------

    a=((1.75^2) +(-2.35^2))^1/2 =2.93m/s^2
     
  8. Nov 24, 2008 #7

    PhanthomJay

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    Now you're catching on! You are exactly right.
     
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