Daily Physicist

Today is the birthday of

• Sir Sandford Fleming (1827-1915)
  
• Émile Borel (1871-1956).

Today’s Problem: Equivalent power of daily 2500 food calories

If a person uses 2500 food calories (kcal) per day, what is their equivalent power output in watts?

A food calorie is 1000 calories, a calorie is 4.184 joules, and a watt is a joule per second. So we can convert food calories to watts like this:

\[\frac{2500 \times 10^3\;\mathrm{calories}}{\mathrm{day}}\left(\frac{4.184\;\mathrm{J}}{\mathrm{calorie}}\right)\left(\frac{1\;\mathrm{day}}{24\cdot 60^2\;\mathrm{sec}}\right) = 121\;\mathrm{J/s} = 121\;\mathrm{W}\]

So a person burning 2500 food calories per day has the power equivalence of a 121 watt light bulb.