Human Power Lab

In this lab we are determining the power output of ourselves from walking up stairs.

In order to perform the lab we are going to need:

• two meter metersticks
• a stopwatch
• kilogram bathroom scale

INTRODUCTION

Power can be described as the rate at which work is done which can also be translated as the rate at which energy is converted from one from to another. To show this we look at the equation:

Change in PE = mgh

where:

• PE is the potential energy
• m is the mass of the object working
• g is the acceleration of gravity
• h is the vertical height gained

We can use this equation to find the change in potential energy which we need because the equation for  power output is:

Power = (change in PE) / (change in time)

 where:

• change in time is the time it takes to climb the vertical height

This is the unit analysis of the lab we are doing. The change in potential energy is read as (kgm^2/s^2) which is the same as Newton meters (Nm) which is equal to Joules.

PROCEDURE:

We first started this lab out by weighing ourselves on a kilogram bath scale. We measured our mass in kg. Once we weighed ourselves, we then went to the stairs that were down the hall from the lab and measured the height from the floor of the first floor to the floor of the second floor. We wanted the height in meters.

This is a sideview of the stairs to show the height we climbed.

We each started at the bottom of the stairs and were timed how long it took to reach the top stair. We performed two trials each for our data.

Once we all collected our two time trials we then calculated our value for our power output. We calculated our value in watts.

Once I found my average Power output in watts, I then solved for it in Horse Power.

DISCUSSION:

I calculated a % difference for what my values were compared to the rest of the class. 

The values I obtained for Power were greater in watts and in Horsepower by more than 10% for each. This meant that I output more power than the average of the class going up the stairs.

Answers to Questions:

1. It is OK to use your hands and arms on the handrailing to assist you in your climb because we are calculating the power our whole body outputs to get us up the stairs as fast as we can. If we use our hands and arms then we are outputing more power to get ourselves up the stairs.\

2. Some problems that can affect the accuracy of this experiment are human error in the stop watch because when told to go the watch isn't started when the person begins to move, it begins when someone says go. People's reaction times are sometimes slower than others. You can also obtain error from the way we measured the height of the stairs. We measured from the floor of the first floor to the half way point where the direction the stairs go is turned around, and then from there to the floor of the 2nd floor.

Conclusion:

I learned in this lab how to find the power output of a person. The process we learned is when something is changing in height. We were able to calculate our power going up the stairs. I output more power than the class average which means I was working harder since our height was all the same and Work can be expressed as m*g*h. I also learned how to apply the % difference when appropriate. We couldn't solve for a percent error because we weren't given an accepted value or a theoretical value to compare from. We only had others' values to compare to. This is why we used percent difference because we could only compare values obtained from fellow classmates.

Answers to Follow Up Questions:

1. They would both produce the same amount of work because they have the same mass, working against the same acceleration due to gravity, and traveling the same height. However, Hinrik would output more power than Valdis because Hinrik does the work faster and Power is a comparison of the amount of work done in a certain amount of time. The longer it takes a person to work, the less power output they will have.

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