Q.

A particle of mass 5m at rest suddenly breaks on its own into three fragments. Two fragments of mass m each move along mutually perpendicular directions with speed v each. The energy released during the process is:          [2019]

1 35mv2  
2 53mv2  
3 32mv2  
4 43mv2  

Ans.

(4)

Let the speed of the third fragment of mass 3m be v'.

From the law of conservation of linear momentum,

3mv'=2mvv'=2v3                       ...(i)

   Energy released during the process is,

K.E.=2(12mv2)+12(3m)v'2=mv2+12(3m)2v29  (Using eqn. (i))

=mv2+mv23=43mv2