Power equals total lifting force times velocity at constant speed

Steps:

• Weight of load: 1000 kg × 9.8 m/s² = 9800 N.
• Total force for hook and load: 9800 N + 1000 N = 10,800 N.
• Power: 10,800 N × 0.5 m/s = 5400 W = 5.4 kW.

Why B is correct:

• Power = F × v, with F as sum of forces for hook (1000 N) and load weight (mg), per work-energy principle for constant velocity.

Why the others are wrong:

• A: Uses only load weight (9800 N × 0.5 m/s = 4.9 kW), ignores hook force.
• C: Approximates load as 10,000 N and doubles velocity (10,000 N × 2 m/s = 20 kW), incorrect values.
• D: Approximates total force as 11,000 N and doubles velocity (11,000 N × 2 m/s = 22 kW), wrong assumptions.

Final answer: B