Question

An `alpha`-particle with a kinetic energy of `2.1eV` makes a head on collision with a hydrogen atom moving towards it with a kinetic energy of `8.4 eV`. The collision
A. must be perfectly elastic
B. may be perfectly inelastic
C. may be inelastic
D. must be perfectly inelastic

Answer 1

Correct Answer - C
`underset(m)(H) underset(4E)to underset(E) larrunderset(4m)(alpha)`
` p_(i)=sqrt(4.4.E)-sqrt(4mE)=0`
For completely inelastic collision both coem to rest after collision and net energy of `4E+E=10.5eV` is lost. But electron in ground state of H-atom can accept only an energy of `10.2eV`. Hence the collision may be inelastic but it can never be perfectly inelastic.