A neutron makes a head-on elastic collision with a stationary deuteron. The fractional energy loss of the neutron in the collision is
16/81
8/9
8/27
2/3
Fractional decrease in kinetic energy of neutron=1−m1−m2m1+m22 [As m1=1 and m2 = 2] =1−1−21+22=1−132=1−19=89