When two objects are in contact and moving together, the following statements must be true:
- The objects must exert the same magnitude force on each other. This is according to Newton's third law, which states that for every action, there is an equal and opposite reaction. So, forces between the two objects are equal in size and opposite in direction.
- The objects must have the same acceleration. Since they are moving together as a single system, no relative motion between them occurs, implying they share the same acceleration.
- If the objects are moving together with no relative motion between them, there is no friction acting between them because friction opposes relative motion.
Thus, the key truths are the equality of forces they exert on each other and sharing the same acceleration when moving in contact together.
