How Long to Climb Three Flights of Stairs?

AI Thread Summary
To determine the time taken to climb three flights of stairs (9.7m), a person weighing 150lbs (667.5N) calculates the work done against gravity as 6474.75J. The average power expended is derived from the work and the time taken, which was estimated at 21.33 seconds. This results in a power output of 248 watts or 0.332 horsepower. The calculations and results are deemed reasonable for the scenario presented. The discussion emphasizes the importance of estimating time for accurate power calculations.
luvlybug1025
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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?
 
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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.
 
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?
 
Pretty reasonable.
 

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