Equilibrium Conditions for Two Forces

Steps:

• Equilibrium requires net force and net torque to be zero.
• For net force zero with two forces, magnitudes must be equal and directions opposite, confirming statement 1 but refuting 2 (same direction yields net force ≠ 0).
• Statement 3 holds because forces must share the same line of action to produce zero torque, meaning they act through the same point.
• Thus, only statements 1 and 3 are correct.

Why B is correct:

• Newton's first law and torque equilibrium dictate equal, opposite, collinear forces for two-force equilibrium.

Why the others are wrong:

• A includes 2, but same-direction forces prevent net force zero.
• C includes 2 but excludes 1, yet unequal magnitudes cannot balance.
• D includes 2, which violates translational equilibrium.

Final answer: B