In the system shown in fig. block of mass M is placed on a smooth horizontal surface. There is a mass less rigid support attached to the block. Block of mass m is placed on the first block and it is connected to the support with a spring of force constant K. There is no friction between the blocks. A bullet of mass `m_(0)`, moving with speed `u` hits the block of mass M and gets embedded into it. The collision is instantaneous. Assuming that m always stays over M, calculate the maximum extension in the spring caused during the subsequent motion.
`K=8960 N//m , u=400 m//s`

Answer

0.1 m