to point A and attach it to the existing spring k, as shown in Figure 10-8b, or we can transfer an equivalent spring keff to point B and attach it to the existing mass m as shown in Figure 10-8c. In either case, for the lumped model to be equivalent to the original system, it must have the same energy in it.
Let's first find the effective mass that must be placed at point A to eliminate the lever. Equating the kinetic energies in the masses at points A and B