A child ascends a staircase four times. The duration of each ascent is noted. Which time is measured when the child’s useful power is at its greatest?
- A$10\,\text{s}$
- B$20\,\text{s}$
- C$30\,\text{s}$
- D$40\,\text{s}$
Physics 0625 · IGCSE · Energy, work and power