## Simple Harmonic Motion Question

I am going brain dead on a rather simple question. Appreciate some help.

A mass of 4.5 KG attatched to a horizontal spring of constan 75 KN/m is compressed 0.4 m from Equilibirium and then a loose mass of 2.5 KG is placed in front of it . IF the mass is now released:

1. at what point do the masses separate.
2. How far apart are they when the 4.5 KG mass stops?

Assume no friction.

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 part 1: the mass moves at the same speed with the spring while they are in contact, so, they will separate at the point when the spring started to slow down (deccelarate) [assuming the spring is ideal, massless, and ignore the effect of gravity] part 2: the mass will not stop if it shoots horizontally... coz you assume no friction... if it shoots vertically, you can use conservation of energy... the energy stored in spring is 1/2 kx^2