Final answer:
The student would gain approximately 17.9 grams of body fat from an excess energy intake of 697.6 kJ, considering a day of minimal activity involving 16 hours of sitting and 8 hours of sleep.
Step-by-step explanation:
The student's question pertains to the conversion of excessive energy intake into body fat as a result of a lack of physical activity to burn off the consumed calories.
To calculate the body fat gain, we first need to determine the total energy expenditure for the day. Here, the person sits relaxed for 16 hours and sleeps for 8 hours. With the energy consumption rates given for these activities (120 W for sitting relaxed and 83 W for sleeping), we can find out how much energy is used in a day.
Energy consumed while sitting relaxed for 16 hours: 120 W * 16 h * 3600 s/h = 6,912,000 J (or 6912 kJ).
Energy consumed while sleeping for 8 hours: 83 W * 8 h * 3600 s/h = 2,390,400 J (or 2390.4 kJ).
Total energy expended: 6912 kJ + 2390.4 kJ = 9302.4 kJ.
If 10,000 kJ is consumed and only 9302.4 kJ is used, the excess energy is 10,000 kJ - 9302.4 kJ = 697.6 kJ.
The amount of fat gained from this excess energy: 697.6 kJ / 39 kJ/g = 17.9 grams of fat.