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Homework Help: Calculate the mass of unknown nucleus

  1. Aug 25, 2004 #1
    OK having a slight problem finding the mass of the unknown nucleus.

    Any help rearranging to find this using Newton's Gravitational law.

    A hydrogen nucleus and a nucleus of an ‘unknown’ atom are stationary, 5.0 x 10 ^-10 m apart. The mass of the hydrogen nucleus is mh = 1.7 x 10 - 27kg and the electric charge of the hydrogen nucleus is e = 1.6 x 10 ^-19 C. You may assume that the electric constant ke, = 9.0 x 10^9N m2 C-2 and that the gravitational constant G = 6.7 x 10^-11N m2 kg -2.

    The magnitude of the gravitational force between the hydrogen nucleus and the ‘unknown’ nucleus is 9.3 x 10 ^-45 N. State whether this force is attractive or repulsive. Calculate the mass of the ‘unknown’ nucleus that is necessary to give a force of this magnitude.

    Thanks in advance

    any help would be great!

  2. jcsd
  3. Aug 25, 2004 #2
    There are many other parts to the question that i have worked . I just need help on rearranging the equation for this part.
  4. Aug 25, 2004 #3

    Doc Al

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    Staff: Mentor

    I assume you know Newton's law of gravity:
    [tex]F = G\frac{m_1 m_2}{r^2}[/tex]

    This can be rearranged to solve for one of the masses:
    [tex]m_2 = \frac{F r^2}{G m_1}[/tex]
  5. Aug 25, 2004 #4
    Yes I know Newtons Law. I already rearranged to this equation but my figures don't seem to add up.

    I have tried a few times now with my calculator and i was missing a minus sign on one the powers.

    I have solved the problem

    Thanks for your help
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