\(=2\,k\)
\(=2 \times 2=4\,N / m \quad m =490\,gm\)
\(=0.49\,kg\)
\(T =2 \pi \sqrt{\frac{ m }{ Keff }}=2 \pi \sqrt{\frac{0.49\,kg }{4}}\)
\(=2 \pi \sqrt{\frac{49}{400}}=2 \pi \frac{7}{20}=\frac{7 \pi}{10}\)
No. of oscillation in the \(14 \pi\) is
\(N =\frac{\text { time }}{ T }=\frac{14 \pi}{7 \pi / 10}=20\)