Final answer:
Both Cart A and Cart B will experience the same force from the wall when they crash into it at 20 miles per hour, due to having the same deceleration upon impact, according to Newton's third law of motion.
Step-by-step explanation:
When both Cart A and Cart B run into a wall at 20 miles per hour, they will experience a force according to Newton's third law of motion. This law states that for every action, there is an equal and opposite reaction. The force on each cart upon impact with the wall depends on its velocity and mass, and both carts have the same velocity. However, in this case, because both carts have different masses, some might initially think that the force exerted by the wall will be different for each cart. Actually, the force experienced by each cart from the wall depends on the acceleration or deceleration of the carts, not just the mass. Since both carts have the same velocity and presumably stop in the same amount of time when they hit the wall, both would experience the same change in velocity, which means they would experience the same amount of force. So, the correct answer is C) Both carts experience the same force.