"A spring with a spring constant of $100$ N$/$m and an original length of $1\mathrm{.}0$ m has one end attached to the ceiling. A $1$ kg mass is hung from the other end of the spring, and the bottom of the mass is supported by hand to keep it stationary

 $($assuming the acceleration due to gravity is $10$ m$/$s$\mathrm{²}).$ If the spring is gradually stretched by supporting the mass from below, the velocity of the mass can be considered as zero during its movement." 

 

  What is the maximum length of the spring? $($ solve using the principle of conservation of mechanical energy?$)"$