A ball of mass `m` is attached to the lower end of a light vertical spring of force constant `K`. The upper end of the spring is fixed. The ball is released from rest with the spring at its normal `(` unstretched `)` length, and comed to rest again after descending through a distance `x`.
A. `x=mg//k`
B. `x=2m g//k`
C. The ball will have no acceleration at the position where it has descended through x/2.
D. The ball will have an upward acceleration equal to g at its lowermost position.
