State the principle of conservation of momentum. - Leaving Cert Physics - Question a - 2005

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:

$m_{1}v_{1} + m_{2}v_{2} = m_{1}v'_{1} + m_{2}v'_{2}$

Where:

• $m_{1}$ and $m_{2}$ are the masses of the two objects,
• $v_{1}$ and $v_{2}$ are their initial velocities,
• $v'_{1}$ and $v'_{2}$ are their velocities after the interaction.