The block has a mass of 0.5 kg and moves within the smooth vertical slot. If the block starts from rest when the attached spring is in the unstretched position at A. determine the constant vertical force F which must be applied to the cord so that the block attains a speed VB = 2.5 m/s when it reaches B: sp = 0.15 m. Neglect the mass of the cord and pulley. -0.3 m- 0.3 m B SB k = 100 N/m C