## Thursday, December 5, 2013

### How much energy do I need to exert to finish my paper?

I have paper that I need to write for, but like most college students, it is the last thing that I want to do.  Being the procrastinator that I am, I want to exert the least amount of force possible to complete the assignment.  I want to determine how much energy must my fingers exert to compete the essay.  Through research I found that the average number of letters in a word is five, so 6 characters per word if I include the space after the word.  My assignment must be 1750 words long which means that it must be approximately 10500 characters longs.  However, I cannot forget about punctuation marks, so I will include an addition 100 characters to cover any periods or commas that I may use for a grand total of 10600 characters.  Now I must determine how much force is required to type one letter.  By quickly looking on the Internet I can easily determine the mass of a penny.  Therefore, I will stack pennies atop one key until the letter appears on my computer screen.  I used a total of 22 pennies that each weighs an average of 2.5 grams that resulted in a total force of 0.54 N.  To determine the a amount of energy required I need to know the distance that the key must depress in order to produce a character on the computer screen.  I estimate this to be about 2.0 mm. Therefore, if Worktotal =  Force x distance then the total amount of energy I need to exert to complete the essay is:

Wtotal= 0.54 x .0020 m x 10600 characters = 11.4 Joules

I also want to determine the rate at which I am exerting this energy, or my power.  Since Power = Work/Δtime and it takes me an average of 3.5 hours to write an essay then my total amount of power is:

P= 11.4 J/3.5 hours x 1 hour/3600 sec = 0.00091 J/s