05-April-2017: Work and Power

Lab 10: Activity - Work and Power
Kevin Nguyen
Lab Partners: Jose Rodriguez, Kevin Tran
Date of Lab Performed: 05 April, 2017

Statement of what the experiment is trying to accomplish: The purpose of the lab was to learn the relationship between work done and power used.

Theory/ Introduction: The idea behind this lab was that we needed to calculate the power that we used from performing several activities, including lifting masses from the ground using a rope and pulley, walking and running up the stairs.

To calculate the power required to lift masses vertically, we needed the distance between the ground and a point where we stopped lifting the mass (think of this as the finish line). The values of the masses were required to calculate work done to lift the mass up. The work done to lift the mass up is defined by "mgh". "M" stands for mass, "g" stands for the gravity constant, and "h" represents the distance from the ground to the finish line. We also recorded the time it took to get the mass form the ground to the finish line since power is defined by "W/t", or work divide by time. Work divided by time will give J/s, or Watts, a measurement of power.

To calculate the power required to walk and run the stairs, we recorded the masses of the person walking and running the stairs. Identical to the previous paragraph, we also used "mgh" to calculate the work done to walk/ run the stairs. The time was recorded for both running and walking the stairs in order to divide work by time. Dividing work by time will give the power done to walk/ run the stairs.

Summary:

The backpacks were set up like the picture below.

The backpack containing the masses was attached to the end of rope, which was set up over the pulley. A person would step on the end of the wooden stick so that the backpack won't pull the stick down. The person at the ground then wore gloves and prepared to pull the rope. Once the timer began, the person pulled the rope until the bottom of the mass passed the bottom of the gate. The same procedure was repeated for the two other masses. Only one person pulled the ropes since having different people pulling the ropes will result in inconsistent data.

For the stairs experiment (both walking and running), the distance from the bottom of the stairs to the top was recorded. The walker/ runner began at rest at the bottom of the stairs. Once the timer began, the person walked/ ran the stairs until they get to the top. The timer stoped once the person got to the top.

A list/table of measured data:

Calculated Results

Conclusion

a) 

The error in the results were not as large as expected. 

b) Assuming that we were running the flight of stairs, which takes 547.5 Watts to climb 4.39 meters, we would have to climb nearly double the height (4.39m times 2 = 8.78 m) in the same amount of time in order to match the amount of power the microwave uses.

c) 1100 Watts * 360 seconds = 396000 Watts

We would have to climb around 3175 meters of stairs per 5.8 second, or 547.4 steps a second, in order to match the power it took to run the microwave.

d) 1) The power is 20833.33 Watts

2) Around 209 people

3) 208.33 seconds