Here's why:

* Momentum is a measure of an object's mass in motion. It's calculated by the formula:

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

* Direct Proportionality: This means if you increase the velocity, you increase the momentum proportionally. If you double the velocity, you double the momentum.

Example:

* A car with a mass of 1000 kg moving at 10 m/s has a momentum of 10,000 kg*m/s.

* If the car's velocity doubles to 20 m/s, its momentum doubles to 20,000 kg*m/s.

Important Note: While momentum is directly proportional to velocity, it's also directly proportional to mass. A heavier object moving at the same velocity will have more momentum than a lighter object.