Here's why:

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

* Momentum (p) = mass (m) x velocity (v)

* Velocity is the rate of change of an object's position with respect to time. A non-moving object has a velocity of zero.

* Therefore, if the velocity is zero, the momentum will also be zero, regardless of the object's mass.