(b) The maximum tension in the string will be at lowest point i.e., Tmax=‌
mv12
I
+mg and minimum tension in the string will be the highest point i.e., Tmin=‌
mv22
I
−mg Therefore, ‌
Tmax
Tmin
=‌
‌
mv12
I
+mg
mv22
I
−mg
=4 ⇒‌‌‌
v12+gl
v22−gl
=4‌‌‌‌‌⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(i) As we know, v12=v22+4gl‌‌‌‌‌⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(ii) So from Eqs. (i) and (ii), we get v22+4gl+gl=4v22−4gl ⇒‌‌3v22=9gl v22=3gl=3×10×‌