Question

The fusion reaction 2H + 2H → 3He + n is initiated by two 2H colliding head-on with equal kinetic energies of 0.124 MeV.

(a) Find the total kinetic energy of the reaction products.

(b) Find the kinetic energy of the neutron.

NOTE: I get A correct which is KE = 3.52 Mev, but for B the answer is 2.64 Mev but I am not getting that. I just need to understand how to do B! Thank you

Answer 1

As you said i am not answering A part.

Now for B part you have to apply conservation of momentum.As there is no force acting on the system the total momentum is conserved.

As two 2H atoms are colliding head on and their kinetic energies are same so their velocities are equal and opposite.Thus total momentum is zero before collision.Here h represents 2H atom.

V_n is velocity of neutron.

Now we know the total kinetic energy from A part.

i.e total kinetic energy

Solving (1) and (2) we get-

Thus 1/2m_nv_n²=2.64 MeV. So kinetic energy of neutron is 2.64 MeV