Lab 10: Activity - Work and power
Author: Tian Cih Jiao
Lab Partners: Weisheng Zhang, Kitarou
Purpose of the lab:
Purpose of this lab is to calculation work and power based on real-life scenarios.
Theory/Introduction:
The first scenario is to lift a known mass up by a measured distance. We are doing this lab outside, where we lift a 5-kg backpack from the first floor to the second floor (top of the balcony). We measure the height of the floor, record the time needed to lift the backpack by pulling the rope. We calculate the power by calculating the work (gravity of the backpack times the height of the balcony) and dividing it by time.
We calculate the power output of someone walking/running up the stairs by using the height and the time of the process.
We measured the height of each stairs and then multiply it to the number of stairs to get the total height.
Measured data:
To get an accurate data of height, we measured three times for a single stair, then we get 6.3, 6.5 and 6.9. We calculated the average of them and get 6.6 inch. And there are 26 stairs. So the total height is 4.37m.
And the time is 11.2 s.
For the walking/running stairs part, we got 12.93 seconds for walking and 5.27 seconds for running.
Analysis:
This is the calculation of how we calculate the power output for lifting a backpack.
This is the calculation of how we calculate the power output for walking/running up the stairs.
Conclusion:
a) Let the speed is constant during walking and running. Then the angle of the slide is 40 degree. Then people travelled is h/sin(40).
Walking average speed = (h/sin(40)) / t(walk) = (4.37m/sin(40)) / 12.93s = 0.526 m/s
Kinetic energy (walking) = 0.5 * Mperson * v^2 = 0.5 * 88 kg * (0.526m/s)^2 = 12.17J
Running average speed = (h/sin(40)) / t(run) = (4.37m/sin(40)) / 5.27s = 1.29 m/s
Kinetic energy (running) = 0.5 * Mperson * v^2 = 0.5 * 88 kg * (1.29m/s)^2 = 73.22J
b) Pmicrowave / Pwalking = 1100/291.47 = 3.77 flights (walk)
Pmicrowave / Prunning = 1100/715.12 = 1.54 flights (run)
c) Pmicrowave * time (in seconds) / Work = 1100 * 360 / 3768.686 = 105.08 flights
d)
(1) 12.5 MJ * 10^6 J/MJ / (10min * 60 s/min) = 20833.3 watts.
(2) 20833.3 watts / 100 watts per person = 209 people 9(can't be 208, must be larger than 208)
(3) 12.5 MJ * 10^6 J/MJ / 100 (J/S) = 125000 second
a) Let the speed is constant during walking and running. Then the angle of the slide is 40 degree. Then people travelled is h/sin(40).
Walking average speed = (h/sin(40)) / t(walk) = (4.37m/sin(40)) / 12.93s = 0.526 m/s
Kinetic energy (walking) = 0.5 * Mperson * v^2 = 0.5 * 88 kg * (0.526m/s)^2 = 12.17J
Running average speed = (h/sin(40)) / t(run) = (4.37m/sin(40)) / 5.27s = 1.29 m/s
Kinetic energy (running) = 0.5 * Mperson * v^2 = 0.5 * 88 kg * (1.29m/s)^2 = 73.22J
b) Pmicrowave / Pwalking = 1100/291.47 = 3.77 flights (walk)
Pmicrowave / Prunning = 1100/715.12 = 1.54 flights (run)
c) Pmicrowave * time (in seconds) / Work = 1100 * 360 / 3768.686 = 105.08 flights
d)
(1) 12.5 MJ * 10^6 J/MJ / (10min * 60 s/min) = 20833.3 watts.
(2) 20833.3 watts / 100 watts per person = 209 people 9(can't be 208, must be larger than 208)
(3) 12.5 MJ * 10^6 J/MJ / 100 (J/S) = 125000 second
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