Question

A uniform circular thin rod of weight w and radius 'r' is pivoted at point B and rest against a frictionless wall at 'A'. Reaction force of wall on circular rod is –

• A. w
• B. w/2
• C. $\frac { 2 \mathrm { w } } { \pi }$
• D. $\left( \frac { \pi - 2 } { \pi } \right) \mathrm { w }$

Answer 1

Answer: (B)

w/2

Answer 2

F_r r = Iα

or μmg cos θ = $\frac { 2 } { 3 } \mathrm { Ma }$

μmg cos θ = $\frac { 2 } { 3 } M \frac { g \sin \theta } { 1 + ( 2 / 3 ) } = \mu = \frac { 2 } { 5 } \tan \theta$ Shortcut

μ = $\frac { \left( \mathrm { I } / \mathrm { MR } ^ { 2 } \right) \tan \theta } { 1 + \left( \mathrm { I } / \mathrm { MR } ^ { 2 } \right) } = \frac { 2 } { 5 } \tan \theta$