Aerobic workout. After a 5-min workout on a Climb Max stair machine, the readout panel (...

Aerobic workout. After a 5-min workout on a Climb Max stair machine, the readout panel (Fig. P6.99) reports that the 75-kg user burned 19.7 Calories (see Problem 85) and climbed a total of 180 steps. (a) If each step is 15 cm in height, how much would the potential energy of the user have changed if she were actually climbing a stairway? (b) What was her rate of change in potential energy? (c) At what rate was her metabolism consuming energy? (d) What is her efficiency in converting the energy in the chemical bonds in her food into potential energy? (e) She really didn’t change her vertical displacement on this machine, so where did that energy go?

(reference problem 85)

Counting calories. The chemical potential energy in foods is measured in units called Calories (notice the capital C). This “food Calorie” is equal to 1000 calories. For example, a typical apple contains approximately 75 Calories, which is actually 75 kilocalories. If all the energy in an apple were converted to gravitational potential energy, how high would you be lifted?