15. In the arrangement shown in figure mA =m and mB=2m, while all the pulleys and string are massless & frictionless. At t=0, a force F=10 t starts acting over central pulley in vertically upward direction. Find.
(a) Time at which both the masses lose contact with floor.
(b) Velocity of A when B loses contact with floor.
[Take all the units into .S.I. System, take m=1 kg and g= 10 m/s2 for part (b)]
