Final answer:
When a small engine car and a massive cargo car are connected and move together, their speeds and magnitudes of acceleration are equal, as per Newton's second law of motion.
Step-by-step explanation:
The question pertains to the relationship between the speeds and accelerations of different parts of a train system. In the given scenario of a train composed of a small engine car and a massive cargo car, if they are connected, then the speed of the small engine car is equal to the speed of the massive cargo car. This is because both cars are attached, and therefore, move together as a single unit. Similarly, the magnitude of the acceleration of the small engine car is equal to the magnitude of the acceleration of the massive cargo car because they are part of the same system and any force applied to the system will accelerate both cars equally, according to Newton's second law of motion.
The speed of the small engine car is equal to the speed of the massive cargo car. The magnitude of the acceleration of the small engine car is equal to the magnitude of the acceleration of the massive cargo car because they are connected and influenced by the same external forces.