The Physics
Opus in profectus

Latent Heat

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  1. Write something.
  2. In order to extract the maximum flavor in the shortest amount of time, your local fast food purveyor has decided to brew its coffee at 90 ℃ and serve it quickly so that it has only cooled down to 85 ℃. While this may be economically sensible, it is negligent and dangerous from a health and safety standpoint. Water (which is what coffee mostly is) at 85 ℃ is hot enough to cause third-degree burns (the worst kind) in two to seven seconds. You decide to add ice cubes to your coffee to cool it down to a more reasonable 55 ℃ so you will be able to drink it sooner. (Watery brew be damned. You need your caffeine now.) How many 23.5 g ice cubes at −18.5 ℃ should you add to your 355 ml cup of coffee to accomplish your thermal goal?
  3. Write something different.
  4. Write something completely different.


  1. The part of a refrigerator responsible for the actual cooling is a closed system of pipes that runs both inside and outside the refrigerator. The substance in the pipes easily changes between the liquid and gaseous phases. Which phase change takes place inside the refrigerator and which take place outside?


  1. A typical hurricane drops 1.5 cm of rain every 24 hours over a roughly circular region 1,300 km in diameter. Given these figures, determine…
    1. the volume of rain precipitated in a day
    2. the mass of rain precipitated in a day
    3. the latent heat released by the condensation of water vapor into raindrops
    4. the power generated by a hurricane

    The total power required for all human activities is something like 12 terawatts.

    1. How many hurricanes are needed to power all human activity?