Torque equilibrium about the hinge Steps:

• Weight acts at midpoint (15 cm from hinge), torque = 5 N × 0.15 m = 0.75 Nm clockwise.
• Tension T acts at rod end (30 cm from hinge) at 40° to horizontal, so angle between T and rod is 40°.
• Torque from T = T × 0.30 m × sin(40°) counterclockwise.
• Set torques equal: T × 0.30 × sin(40°) = 0.75; sin(40°) ≈ 0.643, so T ≈ 0.75 / (0.30 × 0.643) = 4 N. Why B is correct:
• Balances torques using τ = r F sinθ, where θ is angle between position vector and force. Why the others are wrong:
• A: Too low; ignores sin(40°) factor, underestimating lever arm effect.
• C: Overestimates; possibly confuses with vertical force balance without torque.
• D: Too high; approximates T sin(40°) = 5 N directly, ignoring hinge reaction and torque method.

Final answer: B