* Momentum is a measure of an object's mass in motion. It's calculated by the formula: Momentum (p) = mass (m) × velocity (v)

* Equal and Opposite Velocities: Since the balls are traveling at the same speed but in opposite directions, their velocities have the same magnitude but opposite signs. Let's say the speed is 'v', then one ball has a velocity of '+v' and the other has a velocity of '-v'.

* Equal Masses: The balls are identical, meaning they have the same mass ('m').

Calculation:

* Momentum of ball 1: p1 = m × (+v) = mv

* Momentum of ball 2: p2 = m × (-v) = -mv

Total momentum: p1 + p2 = mv + (-mv) = 0

Therefore, the total momentum of the system is zero. This is because the momenta of the two balls are equal in magnitude but opposite in direction, canceling each other out.