Q.

A nucleus with mass number 220, initially at rest, emits an α-particle. If the Q-value of the reaction is 5.5 MeV, calculate the kinetic energy of the α-particle.               [2003]

1 4.4 MeV  
2 5.4 MeV  
3 5.6 MeV  
4 6.5 MeV  

Ans.

(2)

By conservation of momentum, p1=p2

2K1m1=2K2m2               [∵ P=2Km]

⇒2K1(216)=2K2(4)

∴  K2=54K1       ⋯(i)

And given, K1+K2=5.5 MeV     ⋯(ii)

Solving equations (i) and (ii), we get Kα=K2=5.4 MeV