How Long to Climb Three Flights of Stairs?

[luvlybug1025]

Homework Statement

Determine the time it takes to climb three flights of stairs (height = 9.7m). Compute the work done against gravity. Compute the average power expended in watts and in horsepower.

Person = 150lbs.

Homework Equations

h = 9.7m
4.45N/1lb
Avg Power = change in W/change in t
1hp = 746W
F=ma
W = F * d

The Attempt at a Solution

Ok...so, my 150lb=667.5N. That's my F now.
W = f * d = 667.5N * 9.7m = 6474.75J
Once I can find the time it took, then I can use that and the work to find the average power. I just can't figure out how to get time traveled from Work done. Am I on the right track?

 

[kuruman]

You are on the right track. Since the time is not given, you have to come up with a reasonable estimate or climb three flights of stairs and time yourself.

 

[luvlybug1025]

Wow, that makes sense. (I had to measure the stairs myself to.)
Thanks very much for replying so quickly!
I got 21.33s
Work = 5303.8J
Power = 248Watts = 0.332hp
That seems reasonable, right?

 

[kuruman]

Pretty reasonable.