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Force Problem

  1. Feb 14, 2008 #1
    A particle of mass m is initially moving 26.2 m/s. It is brought to rest by a constant net 542 N force in a distance of 69.2 m. Find m, the mass of the particle Assume friction can be ignored.


    the F is 542, i use V(initial)=26.2m/s and V(final)=0m/s S(distance)=69.2 to find A(acceleration). and the answer i got is a=14.886. then i use F=ma, but its wrong, anybody can help?``thank you
  2. jcsd
  3. Feb 15, 2008 #2


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    How did you manage to get a=14.886?? Presumably, m/s^2.
  4. Feb 15, 2008 #3

    Rate of change of momentum = force applied i.e. [m*v]/t=force
    Calculate time using simple kinematic equations.. and then use the above equation....
  5. Feb 15, 2008 #4


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    For the constant force case, [m*v]/t=force is m*dv/dt=force. Or F=ma. I think shenwei1988 knows that.
  6. Feb 15, 2008 #5
    sorry, i am very stupid. still gOt the wrong answer.
    i get 69.2/26.2=2.64=t
  7. Feb 16, 2008 #6


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    You want to use v(final)^2-v(initial)^2=2*a*s to find a.
  8. Feb 16, 2008 #7
    question solved thanks a lot
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