Answer: Both forces are equal each other.
Explanation:
If we assume that no external forces act during the collision (based on the fact that the collision time is very small), total momentum must be conserved, and Newton's 3rd law must apply.
If the total momentum is conserved, the change in momentum for the automobile (caused by the truck) must be equal to the one caused to the truck by the car.
This change in momentum is caused by internal forces, which must be equal each other (even though of opposite signs).
Another way to explain this, is that by Newton's 3rd Law, the force applied by the automobile to the car, must be equal and opposite to the one the truck is applying to the car at the same time.
