Here's how to calculate the magnitude of the car's momentum:

Understanding Momentum

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

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

Applying the Formula

* Mass (m) = 400 kg

* Velocity (v) = 30 m/s

Calculation:

* Momentum (p) = 400 kg × 30 m/s = 12,000 kg·m/s

Answer:

The magnitude of the car's momentum is 12,000 kg·m/s.