Answer:
![t = 0.85 s](https://img.qammunity.org/2020/formulas/physics/high-school/msecvgxh6moxitmtmrn95778u4tqpdhd2n.png)
Step-by-step explanation:
As we know that the block of wood is suspended by spring
Now at equilibrium position we have net force balanced on it
so we have
![mg = kx](https://img.qammunity.org/2020/formulas/physics/college/tiyer85nn9kq6vp1suwxpxyxuifkgzy43d.png)
![0.30 * 9.81 = k(0.02)](https://img.qammunity.org/2020/formulas/physics/high-school/drk2isn8curs78546dkbr2ibv14et8v03c.png)
so we will have
![k = 147.15 N/m](https://img.qammunity.org/2020/formulas/physics/high-school/9tuk6o31xq1qawbpnre4qbbfincmfnjpfh.png)
now the time period of the spring block system for one complete oscillation is given as
![T = 2\pi \sqrt{(m)/(k)}](https://img.qammunity.org/2020/formulas/physics/college/x8m10ij56o71n7ohpzcszjd0nw9u82848l.png)
now plug in all values in it
![T = 2\pi \sqrt{(0.30)/(147.15)}](https://img.qammunity.org/2020/formulas/physics/high-school/2e0wno2pt4fzf15orlmsqwjjggwq1qu4fa.png)
![T = 0.28 s](https://img.qammunity.org/2020/formulas/physics/high-school/5eo1upu3ego6myy2zj8pw916bzrrizap4l.png)
Now total time to complete 3 cycles is given as
![t = 3T](https://img.qammunity.org/2020/formulas/physics/high-school/lm6sx65i3y0fjw6at7r6w37n9xrs1442ek.png)
![t = 0.85 s](https://img.qammunity.org/2020/formulas/physics/high-school/msecvgxh6moxitmtmrn95778u4tqpdhd2n.png)