Question

A 790N person runs up a flight of 40 stairs (.25m for each step) in 20 seconds, and then down 10 steps in 5 seconds. How much total mechanical work is completed? How much total mechanical power is generated? Show all work.

Answer 1

Person moves up 40 stairs and then go down by 10 steps

So total steps that person moves up will be

`N = (40 - 10) = 30 steps`

Each step is of height 0.25 m

so total height raised

`H = 30 * 0.25 = 7.5 m`

Total mechanical energy consumed

`E = mgH`

here we know that

`mg = 790 N`

`E = 790 * 7.5 = 5925 J`

Total mechanical power generated will be

`P = (E)/(t)`

`P = (5925)/((20 + 5))`

`P = 237 W`

so its total power will be 237 Watt