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## Homework Statement

Two masses, M and 4M, are on opposite ends of a massless spring, sitting on a frictionless, horizontal table. The spring is compressed, and the spring-and-masses system is released from rest. If mass M oscillates with amplitude A and frequency f, then mass 4M will oscillate with (HINT: Consider the center of mass!)

## Homework Equations

F=-kx

xcom = 1/MƩx

_{i}m

_{i}

ω

^{2}=k/m

f=ω/2∏

## The Attempt at a Solution

There is no net external force and I'm assuming the system is compressed to its center of mass which means there is a displacement for M of 4L/5 (L being the spring length) and a displacement of L/5 for 4M. So the amplitude of 4M is A/4 because it was displaced 1/4 the distance of M.

Using ω

^{2}=k/m

and f=ω/2∏ I found the frequency of 4M to be f/2. This is wrong acc. to webassign tho so I'm confused if my whole approach is wrong or just my calculations? Thanks