A body of mass m is attached to the lower end of
a spring whose upper end is fixed. The spring has
negligible mass. When the mass m is slightly pulled
down and released, it oscillates with a time period
of 3s. When the mass m is increased by 1 kg, the
time period of oscillations becomes 5 s. The value
of m in kg is :-
(1)16/9
(2)9/16
(3)3/4
(4)4/3