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Homework Help: Work-Energy Scaling

  1. Mar 2, 2005 #1
    A particle of mass [tex]M[/tex] moves along a straight line with initial speed [tex]v_i[/tex]. A force of magnitude [tex]F[/tex]pushes the particle a distance [tex]D[/tex] along the direction of its motion.

    assume that the particle's mass is increased to 3M.

    B.)By what multiplicative factor [tex]R_k[/tex] does the initial kinetic energy increase, and by what multiplicative factor [tex]R_w[/tex] does the work done by the force increase (with respect to the case when the particle had a mass [tex]M[/tex])

    If one of the quantities doubles, for instance, it would increase by a factor of 2. If a quantity stays the same, then the multiplicative factor would be 1.

    You should enter the two factors separated by a comma.

    [tex]R_k,R_w = ___________ [/tex]

    this is what i think:

    to find [tex]R_k[/tex] i must use this formula: 1/2*m*v^2
    to find [tex]R_W[/tex], i must use this formula: W=f*d

    okay, now to find r_k: 1/2*M*v^2 = 3M (cancel everything and get only 3)

    now to find r_w:
    [tex]W = 1/2*M*v_i^2+F*D -1/2*M*v_i^2 = 1/2*3M*v_i^2+F*D -1/2*3M*v_i^2[/tex] <-- i get 0, is this correct?

    i'm pretty sure i'm doing it incorrectly, but i dont know how to correct it. can someone help?
    Last edited: Mar 2, 2005
  2. jcsd
  3. Mar 2, 2005 #2
    what does Rk and Rw correspond? does Rk or Rw ask for the 3M part or the M part??

    Please type out the question exactly how you read it. This doesn't make any sense otherwise.
  4. Mar 2, 2005 #3
    i copied the whole thing (it's online,so i just copied and pasted). but R_K is kinetic energy multiplicative factor and R_w is tk work multiplicative factor

    edit: i just figured it out, thanks anyways
    Last edited: Mar 2, 2005
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