Question

A uniform solid cylinder of mass $M$ and radius $R$ rotates about a frictionless horizontal axle. Two similar masses suspended with the help of two ropes wrapped around the cylinder. If the system is released from test then the tension in each rope will be :

• A. $\frac{Mmg}{M+m}$
• B. $\frac{Mmg}{M+2m}$
• C. $\frac{Mmg}{M+3m}$
• D. $\frac{Mmg}{M+4m}$

Answer 1

Answer: (D)

$\frac{Mmg}{M+4m}$

Tension in the both string will be same.

$mg-T=ma$.......(1)

also Inertia solid cylinder is $M{R}^2/2$

Torque at centre of cylinder due to both string

$2T\times R=I\alpha =M{R}^2\alpha /2$ ....(2)

also, $a=\alpha R$ .......(3)

From equations $\left(1\right),\left(2\right)and\left(3\right)$

we get Tension $T=\frac{Mmg}{M+4m}$