In a collision between an electron and a hydrogen atom, why is it useful to select both objects as the system? Pick all that apply: (1) The total momentum of the system does not change during the collision. (2) The sum of the final kinetic energies must equal the sum of the initial kinetic energies for a two-object system. (3) The kinetic energy of a two-object system is nearly zero. (4) The forces the objects exert on each other are internal to the system and don’t change the total momentum of the system. (5) During the time interval from just before to just after the collision, external forces are negligible.

This law states that the momentum of a particular system before and after the collision is constant if no external force acts on the system.

The law of the conservation of momentum gives the effect of the collision between the electron and the hydrogen atom.

From the law of conservation of momentum, momentum mainly describes the product of velocity and mass. Moreover, the total momentum of a body before and after the collision remains constant. Furthermore, as both the electron and the hydrogen atom have been selected as a system, then their total momentum does not change during the collision.

Also, if the collision is considered elastic, then, the net change in the kinetic energy is also zero.

Thus the following conditions will be applicable, 1) the total momentum of the system does not change during the collision, 2) the sum of the final kinetic energies must equal to the sum of the initial kinetic energies for a two-object system, 4) The forces the object exerts on each other are internal to the system and don’t change the total momentum of the system and 5) during the time interval from just before to just after the collision, external forces are negligible.