Washington College

Physics 100

Home Experiment #8 : Running upstairs and power.

Materials: Ruler and watch.

The work W to lift your body weight mg to a height H is, W  = m*g*H .
Power is defined as work per unit time: Power  = W/t
The basic unit of power is 1 W(watt) = 1 Joule/s.

1. Any scale can be used to find your mass m in kg.

2. Measure the height H between two floors of any building. Do it by measuring the height of one step, then counting the number of steps. Now, walk normally up the stairs and record the time it takes. Repeat one more time. Calculate the power output of your body.

3. Repeat the same process, this time running up as fast as you can. Repeat one more time. What is the power output of your body?

4. Compare the power values in 2 and 3. Why are they so different? If you decide to run three floors up, would these values change ? Why? Try it.

5. Could the power of a slow moving person be larger than a fast moving one? Explain.

6. One h.p. is about 750 watts. Compare the values you obtained with that of a lamp (0.1 h.p.), a vacuum cleaner (0.5 h.p.), or a push lawn mower (5 h.p.). If you were able to exercise to your maximum power for one whole hour, how high would you be able to climb vertically? Does the result make any sense?