Work, Average Power, and Time?

In summary, the task is to determine the time it takes to climb three flights of stairs with a height of 9.7m. The person climbing the stairs weighs 150lbs, which is equivalent to 667.5N. The work done against gravity is calculated to be 6474.75J. To find the average power expended, the time traveled is needed, which can be estimated or measured by physically climbing the stairs. The final result is 21.33s for the time, 5303.8J for the work, and 248 watts or 0.332 horsepower for the average power.
  • #1
luvlybug1025
5
0

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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  • #2
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.
 
  • #3
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?
 
  • #4
Pretty reasonable.
 

1. What is work and how is it related to power and time?

Work is defined as the amount of energy needed to move an object a certain distance. It is directly related to power and time through the equation W = P x t, where W is work, P is power, and t is time. This means that the more power you use or the longer you work, the more work is done.

2. How do you calculate average power?

Average power is calculated by dividing the work done by the time it took to do the work. This can be represented by the equation P = W/t. Average power is measured in watts (W) and is a measure of how much energy is used per unit of time.

3. What is the relationship between power and time?

The relationship between power and time is inverse. This means that as power decreases, time increases and vice versa. This is because power is the rate at which work is done, so the more power used, the less time is needed to complete the same amount of work.

4. How does time affect work done?

The time taken to do a certain amount of work directly affects the amount of work done. The longer the time taken, the more work is done, while a shorter time will result in less work. This is because work is the product of power and time, so the longer the time, the more energy is used to do the work.

5. How can power be increased to do more work in less time?

To increase power and do more work in less time, either the amount of work or the time taken must be increased. This can be achieved by using more energy, such as by increasing the force applied to an object, or by reducing any resistive forces acting on the object. Additionally, using more efficient methods or tools can also increase power and reduce the time needed to do work.

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