(b) Let original length be xcm. Initial angular velocity be ω. Elongation, dx=1cm According to Newton's law F=−kdx=
mv2
r
⇒−kdx=mω2r Since, r=(x+1) and dx=1cm Therefore, −k(1)=mω2(x+1) ...(i) Again angular velocity is doubled and elongation produced is 5cm. Therefore, −k(5)=m(2ω)2(x+5) −5k=4mω2(x+5) From Eq. (i) and Eq. (ii), we get