1. The problem statement, all variables and given/known data Two masses m1 and m2 are joined by a light spiral spring. Each body oscillates along the axis of the spring, which obeys Hooke's law in both extension and compression. The bodies move in opposite directions and the centre of mass of the system is stationary. Explain why the periods of the oscillations of both bodies are the same 2. Relevant equations 3. The attempt at a solution Since the two masses are attached to the same spring, they should exprience the same amount of restoring force F. Hence, F=m1a1=m2a2=kx a1=k/m1x a2=k/m2x Since m1 and m2 are not the same, the value of k/m1 and k/m2 should also not be the same. T = 2pi(k/m)1/2 Following this reasoning, how can the periods of oscillations of both body be the same? I don't understand.