Question

Shown in the figure is rigid and uniform one meter long rod AB held in horizontal position by two strings tied to its ends and attached to the ceiling. The rod is of mass 'm' and has another weight of mass 2m hung at a distance of 75 cm from A. The tension in the string at A is :

(1) 0.75 mg 

(2) 1 mg 

(3) 0.5 mg 

(4) 2mg

Answer 1

Ans. (2) 1 mg

Sol. $\tau$_net about B is zero at equilibrium

T_A 100 – mg × 50 – 2 mg × 25 = 0

T_A 100 = 100 mg

T_A = 1 mg