Two carts are put back-to-back on a track. Cart A has a spring-loaded piston; cart B, which has twice the mass of cart A, is entirely passive. When the piston is released, it pushes against cart B, and the both carts move apart. Which of the two forces exerted by the two carts on each other has a larger magnitude? A. The force exerted by A. B. The two forces have equal magnitude. C. The force exerted by B.

The forces exerted by cart A and cart B on each other are equal in magnitude and opposite in direction. This follows from Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. So, when the spring-loaded piston in cart A is released, it exerts a force on cart B, and cart B exerts an equal force back on cart A. Therefore, the correct answer is B: The two forces have equal magnitude.