A neutron moving with a speed 'v' makes a head on collision with a stationary hydrogen atom in ground state.…

A neutron moving with a speed 'v' makes a head on collision with a stationary hydrogen atom in ground state. The minimum kinetic energy of the neutron for which  perfactly inelastic collision will take place is :
  1. 20.4 eV
  2. 10.2 eV
  3. 12.1 eV
  4. 16.8 eV

Solution

Let velocity before collision v from momentum conservation mv=( m+m ) v 1

v 1 = v 2

Loss in K.E. =12mv2-122mv22

=14 mv2

K.E. lost is used to jump from 1st orbit to 2nd orbit  K.E.=10.2 eV

  14 mv2=10.2

12 mv2=2×10.2=20.4 eV

Asked in: JEE Main 2016 (10 Apr Online)

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