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

A person runs up 40 stairs and then come down 10 steps

So total stairs upwards is given as

`N = 40 - 10 = 30`

now here we will have total height reached

`H = N* h`

`H = 30 * 0.25 = 7.5 m`

Now total energy used or mechanical work done is

`W = mgH`

`W = 790 * 7.5 = 5925 J`

Now the mechanical power is given as

`P = (W)/(t)`

`P = (5925)/(20+ 5) = 237 W`