CGPET 2017 Solved Paper

According to law of conservation of linear momentum mnun+mdud=mnvn+mdvd
Kinetic energy is conserved is head on collision
∴

1

2

mnun2+

1

2

mdud2=

1

2

mnvn2 +

1

2

mdvd2
As deutron is stationary before collision, ud=0 and md=2mn
Substituting these value, we get vd=

2

3

un
=

1 2 mun2− 1 2 mvd2

1 2 mun2

=

8

9