Bill Goodwine's Courses

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Hi Dr. Goodwine,

I was looking through solution 7.4 and part of it is confusing to me. When I looked at the equations of motion for the second mass on the third spring, it seems to be that the spring force does not depend on the location of mass 3, which is assumed to be there. The same goes with the velocities and dampers, and this pattern propagates through the solution. Shouldn't there be something about the location and velocity mass 3 in the solution? Or was it wrong to assume that there is a mass there? Thanks!

cdiberna wrote:Hi Dr. Goodwine,

I was looking through solution 7.4 and part of it is confusing to me. When I looked at the equations of motion for the second mass on the third spring, it seems to be that the spring force does not depend on the location of mass 3, which is assumed to be there. The same goes with the velocities and dampers, and this pattern propagates through the solution. Shouldn't there be something about the location and velocity mass 3 in the solution? Or was it wrong to assume that there is a mass there? Thanks!

You are right. I'll ask the grader to fix it (if he has time...)