Work by tension equals force component along displacement

Steps:

• Identify displacement as horizontal 20 m; tension acts at 40° to horizontal.
• Horizontal component of tension: 200 N × cos(40°) ≈ 200 × 0.766 = 153.2 N.
• Work done: 153.2 N × 20 m = 3064 J = 3.1 kJ.
• Vertical component does no work as displacement is horizontal.

Why B is correct:

• Matches work-energy theorem: W = F ⋅ d = T cos θ × d, where θ is angle between force and displacement.

Why the others are wrong:

• A: Underestimates by using sin(40°) instead of cos(40°).
• C: Overestimates by approximating cos(40°) as 0.85.
• D: Assumes full tension without angle adjustment.

Final answer: B