We know that, torque, τ=Iα...(i) If T is the tension in the string, then τ=TR....(ii) From Eqs. (i) and (ii), we get α=TR Under no slipping condition, α=‌
a
R
Hence, I⋅‌
a
R
=TR⇒T=‌
lâ‹…a
R2
For cylinder, I=‌
MR2
2
∴‌‌T=‌
MR2
2
⋅‌
a
R2
⇒T=‌
ma
2
....(iii) For the motion of the block, Mg−T=Ma ⇒‌‌Mg−‌