A block of mass
m placed on a smooth floor is connected to a fixed support with the help of a spring of stiffness
k. It is pulled by a rope as shown in the figure. Tension force
T of the rope is increased gradually without changing its direction until the block losses contact from the floor. The increase in rope tension
T is so gradual that acceleration in the block can be neglected. What is the extension in the spring, when the block losses contact from the floor?