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Q5.17 A nucleus is at rest in the laboratory frame of reference. Show that if it disintegrates into two smaller nuclei the products must move in opposite directions.

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Let the mass of parent nuclei be m.

And the mass of daughter nuclei be mand m2.

Initial momentum is zero since the nuclei is at rest.  

But after dissociation, the momentum becomes : 

                                                       M\ =\ m_1\ v_1\ +\ m_2 v_2

Using conservation of momentum,

                                                        0\ =\ m_1\ v_1\ +\ m_2 v_2

or                                                     v_1\ =\ \frac{-m_2 v_2}{m_1}

Thus both velocities have opposite direction.

Posted by

Devendra Khairwa

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