A worker lifts a 5 kg weight by 2 m in 2 s. What is the average power in watts? (g ≈ 9.8 m/s^2)

A worker lifts a 5 kg weight by 2 m in 2 s. What is the average power in watts? (g ≈ 9.8 m/s^2)

• A. 24.5 W
• B. 49 W
• C. 98 W
• D. 196 W

Answer: (B)

Power is the rate at which work is done. When you lift a mass against gravity, the work you do goes into increasing its gravitational potential energy, so the work equals m g h. Compute the energy gain: m g h = 5 kg × 9.8 m/s^2 × 2 m = 98 joules. The time taken is 2 seconds, so the average power is work/time = 98 J / 2 s = 49 watts. Thus, the average power is 49 W.

Power is the rate at which work is done. When you lift a mass against gravity, the work you do goes into increasing its gravitational potential energy, so the work equals m g h.

Compute the energy gain: m g h = 5 kg × 9.8 m/s^2 × 2 m = 98 joules.

The time taken is 2 seconds, so the average power is work/time = 98 J / 2 s = 49 watts.

Thus, the average power is 49 W.