Here's why:

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

* Mass is a fundamental property of matter that represents its resistance to acceleration.

* Velocity is the rate of change of an object's position with respect to time, incorporating both speed and direction.

Therefore, for an object to have momentum, it must have both mass and velocity. If an object is at rest (velocity = 0), its momentum is zero. Similarly, if an object has no mass, it cannot have momentum.