# Collision in Spring-mass System-1!

Two bodies $$A$$ and $$B$$ of mass $$m$$ and $$2m$$ respectively are placed on a smooth floor. They are connected by a spring of negligible mass. A third body $$C$$ of mass $$m$$ is placed on the floor. The body $$C$$ moves with a velocity $$v_0$$ along the line joining $$A$$ and $$B$$ and collides elastically with $$A$$. At a certain time after the collision it is found that the instantaneous velocities of $$A$$ and $$B$$ are same and the compression of the spring is $$x_0$$. The spring constant $$k$$ will be :

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