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
`P_(i) = sqrt(m.4.E) - sqrt(4mE) = 0`
For completely inelastic collision both cone to rest after collision and net energy of `4E + E = 10.5 eV` is lost. But electron in ground state of `H`-atom can accept only an energy of `10.2 eV`. hence the collision may be inelastic but it can never be perfectly inelastic.