Effective mass (spring–mass system)

In a real spring–mass system, the spring has a non-negligible mass m {\displaystyle m} . Since not all of the spring's length moves at the same velocity v {\displaystyle v} as the suspended mass M {\displaystyle M} (for example the point completely opposed to the mass M {\displaystyle M} , at the other end of the spring, is not moving at all), its kinetic energy is not equal to 1 2 m v 2 {\textstyle {\frac {1}{2}}mv^{2}} .

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