Question

Suppose a gas particle is moving toward the right wall of a container. Its velocity com- ponents before the wall collision are vx, vy, and vz. What are its three velocity components after it undergoes an elastic collision with the right wall?

Answer 1

An elastic collision is one where the kinetic energy of the particle undergoing collision remains the same before and after the collision. In other words, there is no conversion of kinetic energy and the kinetic energy is conserved.

We have chosen the Cartesian co-ordinate system for our reference. The velocity components of the particle are v_x,v_y and v_z. Since the particle undergoes elastic collision, the magnitude of the velocity components will remain the same, but the direction will be reversed. In other words, the particle will move toward the left with velocity components (–v_x), (-v_y) and (–v_z), i.e, the velocity components will be reversed.