Bob B of mass m at rest is hanging vertically from the ceiling via a massless string of length 10 m, as shown in the figure. Point mass A of mass m travelling horizontally with speed $10~ms^{-1}$ hits bob B elastically. The bob B rises h meter after the collision. Taking the acceleration due to gravity $g=10~ms^{-2}$ and neglecting the size of the bob, the value of h is: [Image Placeholder]