Power as force times velocity against gravity

Steps:

• Calculate weight force: F = mg = 600 kg × 9.8 m/s² = 5880 N.
• Convert speed to m/s: v = 12 m/min ÷ 60 = 0.2 m/s.
• Compute power: P = F × v = 5880 N × 0.2 m/s = 1176 W.
• Convert to kW: 1176 W = 1.176 kW ≈ 1.2 kW.

Why B is correct:

• Matches the formula for useful power output P = Fv, where F is gravitational force and v is constant velocity, giving the rate of work against gravity.

Why the others are wrong:

• A: Uses speed in m/min without converting to m/s, yielding 0.118 kW.
• C: Applies incorrect g=10 m/s² and miscalculates v as 2 m/s, giving ~7 kW.
• D: Approximates with g=10 but forgets to divide by 1000 for kW, or uses v=0.1 m/s.

Final answer: B