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A nucleus of uranium decays at rest into nuclei of thorium and helium. Then:

  1. A
    The helium nucleus has less kinetic energy than the thorium nucleus
  2. B
    The helium nucleus has more kinetic energy than the thorium nucleus
  3. C
    The helium nucleus has less momentum than the thorium nucleus
  4. D
    The helium nucleus has more momentum than the thorium nucleus

Solution & Step-by-step Explanation

By conservation of momentum, since the uranium was at rest, the magnitudes of momenta of thorium () and helium () must be equal: .Kinetic energy .Since is the same, .The mass of the helium nucleus (alpha particle) is much smaller than the thorium nucleus, so the helium nucleus has more kinetic energy.

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A nucleus of uranium decays at rest into nuclei of thorium and helium. Then:
A
The helium nucleus has less kinetic energy than the thorium nucleus
B
The helium nucleus has more kinetic energy than the thorium nucleus
C
The helium nucleus has less momentum than the thorium nucleus
D
The helium nucleus has more momentum than the thorium nucleus

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