[填空题]
A 1.68-kg mass oscillates on the end of a spring w1)4tj7 qn0ugy ut 2s ium2ts+4k jbn(zhprhn)r lycf 1k80u )b1ose spring stiffness constant isl)u kp01b y n)1chf8rr $k=48.7 \, \text{N/m}$. 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
