1. Find the acceleration:

* Initial velocity (v₁): 15 m/s west

* Final velocity (v₂): 30 m/s west

* Time (t): 10 seconds

* Acceleration (a) = (v₂ - v₁) / t

* a = (30 m/s - 15 m/s) / 10 s

* a = 1.5 m/s² west

2. Calculate the net force:

* Mass (m): 4000 kg

* Acceleration (a): 1.5 m/s² west

* Net force (F) = mass (m) * acceleration (a)

* F = 4000 kg * 1.5 m/s²

* F = 6000 N west

Therefore, the net force on the car is 6000 Newtons in the westward direction.