The Physics of Work and Energy

I walked into Physics class today to find Michael Jorgensen, our Science and Math teacher, calculating the amount of energy generated by stepping up onto a chair. His class is in the middle of a work and energy unit, and they wanted to move beyond the textbook to see how much energy it takes to move our daily lives. For instance, the microwave in our kitchen uses 1,200 watts, while the iPad charger students were using to take notes uses just 10 watts. Noting the vast difference, Whitney of Seattle, Washington asked, “so should we charge our iPads with a microwave?” For the record, that would be an ill-advised strategy.  

Jorgensen then turned the students loose to investigate their own exercises. Wilson of Evergreen, Colorado wanted to find out the amount of energy created doing a simple daily task, so he timed himself running up the stairs in the Confluence Building. He generated 550 watts: enough to power a large home entertainment system.

Jasper of Portland, Oregon focused on generating energy with pushups to prove his power to Jorgensen, who also serves as our PE teacher. In a 15 second burst, he completed 18 pushups and generated 193 watts: comparable to the draw of an XBox 360 or a mini fridge. Jasper lamented the fact that he had produced less energy than Wilson. Jorgensen responded with a leading question: “which muscles did you use to do a pushup versus climbing the stairs?” 

Gigi of Charlotte, North Carolina measured the energy created by moving her arm up and down (seen here in a Summit Dance in the Owyhees in Spring 2017). A relatively small weight moved over a shorter distance, for a grand total of 19 watts: enough energy to power a ceiling fan on low.

To put this all into perspective, in order to power the appliances mentioned above, students would need to carry out the activity continuously for as long as they wanted to use it. Moreover, the cost of energy from the outlet is 12 cents per Kilowatt hour nationally and 9 cents in Idaho. If Wilson ran up stairs for an hour straight, he would produce approximately 5 cents worth of energy for campus. At the end of class, I asked the group for some conclusions. Could Jasper use push-ups to power his XBox for a whole hour? “I couldn’t even do it for a minute!”