Question

1.) A dietician develops a new diet, in which people drink copious amounts of ice water. The theory is that the body must raise the temperature from 0.0 deg C to body temperature (37.0 deg C), and will use energy (therefore burning fat) to achieve this. If it takes 3500 Cal (3500 kcal) of energy output to burn off 454 g (about 1 pound) of fat, how much ice water (in L) must be consumed to achieve this? (Useful information: 1 L = 1000 cm³; density of water = 1 g/cm³; specific heat of water = 1 cal/g deg C)

2.) An inventor develops a stationary cycling device by which an individual, while pedaling, can convert all of the energy expended into heat for warming water. How much mechanical energy is required to increase the temperature of 300 g of water (enough for one cup of hot chocolate) from 20 deg C to 95 deg C? (Water has a specific heat of 4186 J/kg deg C.)

3.) A mediocre cyclist can produce 150 J of energy per second. How long (in minutes) would it take this cyclist to heat the cup of water in the previous problem for hot chocolate?

Answer 1