Force equilibrium on stationary nail

Steps:

• Weight W acts vertically downward.
• Tension T acts at 40° to vertical, with upward vertical component T cos 40° balancing W and horizontal component T sin 40° away from wall.
• Reaction R acts horizontally toward wall, equal to T sin 40° for horizontal equilibrium.
• Correct diagram shows vectors to scale: W down, T angled 40° up from horizontal pull, R horizontal opposite T's horizontal component, summing to zero.

Why A is correct:

• Matches equilibrium: vertical components balance (T cos 40° = W), horizontal R = T sin 40°, per Newton's first law.

Why the others are wrong:

• B: Incorrect T angle, misaligns components.
• C: Wrong R direction, disrupts horizontal balance.
• D: Magnitudes not to scale, vertical forces unequal.

Final answer: A