Engineering
The power of your legs
Estimate the power you produce running up one flight of stairs. Choose your own numbers and tell me what you are ignoring.
- Hint 1Power = work done ÷ time. The work done against gravity is mgh.
- Hint 2A flight of stairs climbs roughly one storey, about 3 m.
- Take a 70 kg person, a 3 m climb, and 5 seconds.
- Work against gravity = 70 × 9.8 × 3 ≈ 2,100 J.
- Power ≈ 2,100 ÷ 5 ≈ 400 W.
- This ignores the energy used swinging legs and arms and the body's inefficiency, so the food energy burned is several times larger.
Where it lands: Roughly 400 W (for 70 kg, 3 m, 5 s).
The trap: Using the length of the staircase instead of its height.
What a tutor might ask next: How long could you keep that power up, and how does it compare with a kettle?
Now do one out loud. In the interview you think aloud with a tutor. Try an Engineering problem with hints, follow-ups and Mia's feedback on how you think.