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F=ma problem, I feel retarded because I can't get it

  1. Feb 3, 2009 #1
    Seriously I feel so stupid because I can't get the answer to the second part of the problem, what am I doing wrong?

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

    2 parts to the problem:

    An empty truck whose mass is 1500 kg has a maximum acceleration of 1.4 m/s^2 . What is the maximum force that accelerates the truck? ______N

    What is the maximum acceleration when it is carrying a 500 kg load? (hint: same force, but new total mass) ______m/s^2

    2. Relevant equations


    3. The attempt at a solution

    This is for a web based quiz and I got the first part right, it's obviously 2100 N, so then I figured: ok, so to find the acceleration using the same force just solve for a, therefore it should be 2100 N/500 kg, which gives me an answer of 4.2 m/s^2. It's telling me the 2100 N is correct, but not the 4.2 m/s^2 ... what am I doing wrong or not taking into consideration? It's so easy I'm just missing it...
  2. jcsd
  3. Feb 4, 2009 #2
    Force = TOTALmass * acceleration

    What is the TOTALmass
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