I am a little bit confused about the implication from my computation. Must have done something wrong in the computation.
Assume we hold the top end of the mass-spring-mass system in the air, and the system is at equilibrium. Now release the top end mass to let the system have a free fall, what would be the tension in the spring (assume massless) ? I solve a simple ODE and it turns out the tension is given by a sinusoid with magnitude the initial tension.
However, this seems against intuition. I must have solved the wrong ODE...I could have done better with the drawing but I'm lazy.
I'm confused because some people told me accelerometer is based on this principle...what would the accelerometer read in this case...