An a-particle of mass m suffers onc-dimensional elastic collision with a nucleus at rest of unknown mass. It is scattered directly backwards losing 64% of its initial kinetic energy. The mass of the nucleus is (a) 1.5 m (b) 4 m (c) 3.5 m (d) 2 m
Dear candidate, since it's elastic collision so by law of conservation of momentum -
mv0=mv2−mv1
12m(V1) ^2=0.36×12m(V0) ^2
v1=0.6v0
12m(V2)^ 2×0.64×12m(V0) ^2
V2=sqrt(mM) ×0.8V0
mV0=sqrt(mM)×0.8V0−m×0.6V0
⇒1.6m=0.8sqrt(mM)
4m^2=mM
Therefore the value of mass is 4
All the best
Hope this helps