A large truck and a car, both moving with a velocity of magnitude v, have a head-on collision, and both of them come to a halt after that. If the collision lasts for one second, which vehicle experiences the greater force?

According to Newton's third law of motion, the force of impact experienced by both vehicles will be equal and opposite. When the car collides with the truck, it exerts a force on the truck in one direction, and the truck exerts an equal force on the car in the opposite direction. As a result, both vehicles experience the same magnitude of force during the collision. 

However, due to their different masses, they will have different accelerations, which is why the car might experience a more significant change in velocity during the collision compared to the truck. Nevertheless, the forces themselves are equal in magnitude but opposite in direction.

Therefore, we can say 'The truck and the car experience equal forces'.