State the principle of conservation of momentum. - Leaving Cert Physics - Question a - 2008

The principle of conservation of momentum states that in a closed system, the total momentum before an interaction is equal to the total momentum after the interaction. Mathematically, this can be expressed as:

$m_1 u_1 + m_2 u_2 = m_1 v_1 + m_2 v_2$

where:

• $m_1$ and $m_2$ are the masses of the objects,
• $u_1$ and $u_2$ are their initial velocities,
• $v_1$ and $v_2$ are their final velocities.

This principle holds true provided that no external forces are acting on the system.