IB Human Power Output

Option 1: Human Power Output

Purpose: To measure your human power output.

Materials: Stairs, stadium stairs, stopwatch, meter sticks, kilogram scale, awesome knowledge of physics.

Procedure: You must come up with your own procedure within a group of two or three. Every person should calculate their own power output independently. Be sure to do multiple trials. (3-10??) You could run (or walk) up the stadium stairs (P = mgh/t) You could do pull ups, bench press, sit ups (P = mgh/t) (I would time 10 repetitions, and divide the time by ten to get the time for one rep) You could use a bathroom scale and push a car in the parking lot (P = Fv). Convert the pounds to Newtons, the speed to m/s, and you would then have Watts. You could time someone speeding up from rest to their max speed. (Time that part only) (P = ¹/₂mv²/t)

Your completed lab must have the following:

• Brief description of your procedure

•Diagram of your procedure with distances and quantities you measured labeled.

•Your formulas in a general form.

•An example of how you calculated the power

•A calculated uncertainty of the power output.

You will need to work with other people to gather the data most likely, but the power output you calculate must be your own, and you must turn in your own lab.

Example Calculations:

7:55 Human Power Output

(I show how to do power calculations, and the uncertainty)

Pandemic Lab:

If you go up a flight of stairs, you are doing work, and we can measure that work by knowing your mass, and the height of the stairs. (W = PE = mgh). Now if we know the time it takes you to climb the stairs, we can then calculate your power output. (P = W/t). That is what this lab is about.

You can do this either in pen/pencil and paper, and submit a photo, or as a pdf from a Google doc.

Directions:

1. Find a set of stairs and time how long it takes you to climb them. Do this 5 times and record your times. Try to go the same speed all 5 times.

2. Estimate or measure your weight in pounds, and divide this by 2.2 to get your mass in kilograms. (assuming you are on Earth) Also estimate the uncertainty of this number. (Just make it up)

3. Measure the total height of the flight of stairs in inches, and multiply by 2.54 to get centimeters, and then divide by 100 to get meters. Record the height of the stairs in meters, as well as an estimated uncertainty of this measurement.

4. Calculate the average time and the uncertainty of the time (High - Low)/2 (watch the video?)

5. Make a neat data table labeled with units to summarize all the data and calculations in steps 1-4 above. A neat data table has straight lines around the data (use a straight edge, or google docs) and includes the data, its units, and the uncertainty of the data. If you are using Google docs just use an actual table. You can modify a table from a straight up grid to custom by Insert>Table>drag, and then modify the table using Format>Table>Merge Cells etc.

6. Calculate your best guess power output, as well as the uncertainty of your power output in Watts. Show these calculations clearly and neatly. (So I can be sure you are doing them correctly....) If you are using Google docs you need to show these calculations with the formula editor. (Insert>Equation>fraction) To adjust the size of your formula, select it, and change the Font Size.

If you are using Google docs for the lab - use the formula editor to make the calculations look nice like this: I am not going to accept flattened calculator looking calculations like (34)(56)/(2.31)

7. Answer this question: When we would do this assignment with the stadium stairs on the visitor side of the soccer field, big athletic people would very often get correctly calculated power outputs of 800 to 1400 watts, which is well above a horsepower (745.7 Watts) even with uncertainty taken into account. Are these people really more powerful than a work horse? How do you explain this? (Keep in mind that the times were around 3-4 seconds to run up those stairs)

8. Submit a photo of your work, or a pdf of your Google Doc.

Here are some support videos:

Steps 1-3: <Video for Mass and Height>

Step 4: <Video for Time>

Step 5: <Video for Data Table>

Step 6: < Video for Power> <Video for Uncertainty of Power> <Video Google Equation Editor>