[填空题]
A 1.68-kg mass oscillates on the e-swv f3,bt+m (oh8igqnd of a sprinm5wostzk 2bu;,n rd :tib7e 1(j2 djs*g whose spring stiffness constant (r zjt5 ;1ssdbi jd*22nbmku eot,w7 :is $k=48.7 \, \text{N/m}$. If this system is in a spaceship moving past Earth at 0.900c, what is its period of oscillation according to
(a) observers on the ship, T = s
(b) observers on Earth? $T_{earth}$ = s
