A nucleus of uranium decays at rest into nuclei of thorium and helium. Then,

(a) the helium nucleus has more kinetic energy than the thorium nucleus

(b) the helium nucleus has less momentum than the thorium nucleus

(c) the helium nucleus has more momentum than the thorium nucleus

(d) the heium nucleus has less kinetic energy than the thonum nucleus

U238
   92
->Th238 + He4
        92        2
According to law of conservation of linear momentum, we have.

|PTh|=|PHe|=P

=>As, kinetic energy of an element,

KE=P2/2m

where,m is mass of an element 

Thus,KE∝1/M

So, MHE<MTh=>KHe>KTh

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