Question

An equilateral triangular frame is made of three thin massless rods. Three point masses of mass 'm' each are fixed at vertices of frame as shown. The system is rotated with uniform angular speed w about an (fixed) axis passing through A and normal to plane of triangular frame. Neglect the effect of gravity. The tension in rod connecting mass B and C is –

• A. mw²l
• B. $\frac { m \omega ^ { 2 } \ell } { 2 }$
• C. $\frac { \sqrt { 3 m \omega ^ { 2 } \ell } } { 2 }$
• D. Zero

Answer 1

Answer: (D)

Zero

Answer 2

B moves in dotted circle of radius l with uniform speed. Massless rod 1 can exert force T₁ on B only along its length. Hence T₁ contributes only to centripetal acceleration of B. The tension in rod 2, that is, T₂ can contribute to both tangential and centripetal acceleration of B. Since tangential acceleration of B is zero.

Hence T₂ = 0.