What is the average power required to lift a 6 kg mass through 3 meters in 2 seconds, using g ≈ 9.8 m/s^2?

What is the average power required to lift a 6 kg mass through 3 meters in 2 seconds, using g ≈ 9.8 m/s^2?

• A. 176.4 W
• B. 88.2 W
• C. 44.1 W
• D. 882 W

Answer: (B)

Power when lifting against gravity is the rate at which you do work, and that work is the gain in gravitational potential energy. The work required to raise a mass m by height h is W = m g h, so the average power over a time t is P_avg = W / t = m g h / t. With m = 6 kg, g ≈ 9.8 m/s^2, h = 3 m, and t = 2 s, the work is W = 6 × 9.8 × 3 = 176.4 J, and the average power is 176.4 J / 2 s = 88.2 W. This matches the answer.

Power when lifting against gravity is the rate at which you do work, and that work is the gain in gravitational potential energy. The work required to raise a mass m by height h is W = m g h, so the average power over a time t is P_avg = W / t = m g h / t. With m = 6 kg, g ≈ 9.8 m/s^2, h = 3 m, and t = 2 s, the work is W = 6 × 9.8 × 3 = 176.4 J, and the average power is 176.4 J / 2 s = 88.2 W. This matches the answer.