Q51 / 60 · JEE Advanced 2015 (Paper 2) · Physics

A fission reaction is given by U92236→Xe54140+Sr3894+x+y , where x and y are two particles. Considering U92236 to be at rest, the kinetic energies of the products are denoted by KXe, KSr, Kx(2 MeV) and Ky2 MeV , respectively. Let the binding energies per nucleon of U92236, Xe54140  and Sr3894 be 7.5 MeV, 8.5 MeV, and 8.5 MeV respectively. Considering different conservation laws, the correct option(s) is (are)

  • Correct answer
    A
    x=n, y=n, KSr=129 MeV, KXe=86 MeV
  • B
    x=p, y=e-, KSr=129 MeV, KXe=86 MeV
  • C
    x=p, y=n, KSr=129 MeV, KXe=86 MeV
  • D
    x=n, y=n, KSr=86 MeV, KXe=129 MeV

Solution

U→Xe+Sr+x+2   y2
Q=4+KXe+KSr ...(i)
-Q=EB=236×7.5-140×8.5-94×8.5
∴Q=219 ...(ii)
∴KXe+KSr=215 MeV
Since, both x & y have same KE
∴ both particles should have same mass & lighter body will have higher KE.

Hence, the correct answer is option: 'A'.

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