A 40 kg student gains 5 m in height in 20 s. What is the average mechanical power against gravity? Take g = 9.8 m/s².

Explanation

The increase in gravitational potential energy is mgh = 40 × 9.8 × 5 = 1960 J. Dividing by 20 s gives average mechanical power of 98 W. This is useful mechanical output against gravity, not the student’s total metabolic power.