\(y =-0.21 \sin ( x +30 t )\)
\((x\) in meter \(\&\) \(t\) in sec)
\(v =\frac{\omega}{ k }=\frac{30}{1}=30 m / s\)
\(v =\sqrt{\frac{ T }{\mu}} \Rightarrow T = v ^{2} \mu=(30)^{2}(0.0135)\)
\(=12.15\)
\(= x \times 10^{-2} N\)
\(\Rightarrow x =1215\)