Question

A spool of mass `M` and radius `2R` lies on an inclined plane as shown in the figure. A light thread is wound around the connecting tube of the spool and its free end carries a weight of mass `m`. The value of `m` so that system is in equilibrium is

A. `2Msinalpha`
B. `Msinalpha`
C. `2Mtanalpha`
D. `Mtanalpha`

Answer 1

Correct Answer - A
Equlibrium of `m` gives
`T=m(LT=` tension in string)
Net torque about point of contact of spool should be zero.
Hence `(2R)(Mgsinalpha)=TR`
or `2Mgsinalpha=mg`
or `m=2msinalpha`