Two types of inelastic collision:
If the sum of the kinetic energies of the colliding bodies or particles after collision is not the same as the sum of the kinetic energies of that colliding bodies or particles before collision, then this type of collision is said to be inelastic collision. So there are two possibilities, either there may be an increase in kinetic energy of the colliding particles after collision, or there may be a decrease in kinetic energy of the colliding particles after collision. These two cases give rise to two types of inelastic collisions \( \cdots \)
(i) Endoergic collision:
In case of macroscopic bodies, the loss of kinetic energy occurs as heat, sound, etc. On the other hand, in case of microscopic bodies such as atoms, molecules, etc., the kinetic energies may be absorbed by the atoms and as a result these atoms moves into an excited state. Let the two masses \( m_1 \) and \( m_2 \) moving with velocities \( u_1 \) and \( u_2 \) respectively collide with each other, let \( v_1 \) and \( v_2 \) be the velocities of the respective masses after collision, the kinetic of the particles is then reduced and we can write, \( \frac{1}{2}m_1{u_1}^2+\frac{1}{2}m_2{u_2}^2=\frac{1}{2}m_1{v_1}^2+\frac{1}{2}m_2{v_2}^2+E \), where \( E \) is the excitation energy.
Therefore the sum of the kinetic energies of the colliding particles after collision is less than the sum of the kinetic energies of the colliding particles before collision. This type of collision is known as endoergic collision.
(ii) Exoergic collision:
When the atoms are already in the excited state and they come down to the normal state after collision, then we can write
\( \frac{1}{2}m_1{u_1}^2+\frac{1}{2}m_2{u_2}^2+E=\frac{1}{2}m_1{v_1}^2+\frac{1}{2}m_2{v_2}^2 \), where, \( E \) is the excitation energy.
Therefore the sum of the kinetic energies of the colliding particles after collision is greater than the sum of the kinetic energies of the colliding particles before collision. This type of collision is known as exoergic collision.