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Physics and Astronomy Outreach Program at the University of British Columbia

Human Body Bicycling and Calories. Multiple-Choice Questions. Physics and Astronomy Outreach Program at the University of British Columbia. Bicycling and Calories. Assumptions. In the following questions we assume students know:

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Physics and Astronomy Outreach Program at the University of British Columbia

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  1. Human Body Bicycling and Calories Multiple-Choice Questions Physics and Astronomy Outreach Program at the University of British Columbia

  2. Bicycling and Calories Assumptions • In the following questions we assume students know: • humans need 1500-2500 kcal/day depending on age, gender, and activity level. • one food calorie (1 Cal) is equal to 1 kcal (1000 cal). Physics and Astronomy Outreach Program at the University of British Columbia

  3. Bicycling and Calories Question 1 A cereal bar contains 200 food calories in 50 grams. Which of the following sources has a heat of combustion that is closest to that of the cereal bar? Natural Gas (methane) ~ 55 MJ/kg Kerosene ~ 45 MJ/kg Coal ~ 30 MJ/kg Wood ~ 16 MJ/kg Physics and Astronomy Outreach Program at the University of British Columbia

  4. Bicycling and Calories Question 1 Answer A cereal bar contains 200 food calories in 50 grams. Which of the following sources has a heat of combustion that is closest to that of the cereal bar? Natural Gas (methane) ~ 55 MJ/kg Kerosene ~ 45 MJ/kg Coal ~ 30 MJ/kg Wood ~ 16 MJ/kg Physics and Astronomy Outreach Program at the University of British Columbia

  5. Bicycling and Calories Question 1 Solution A cereal bar contains 200 food calories in 50 grams. Which of the following sources has a heat of combustion that is closest to that of the cereal bar? 200 Calories = 200 kcal (200 kcal)(4200 J/kcal) = 8.4 x 105 J 8.4 x 105 J / 0.05 kg = 17 MJ/kg Therefore, it is comparable with wood. Physics and Astronomy Outreach Program at the University of British Columbia

  6. Bicycling and Calories Question 2 Approximately how long could you live off a cereal bar containing 200 Calories? 30 min 1 h 2-3 h 5-6 h More than 6 hours Physics and Astronomy Outreach Program at the University of British Columbia

  7. Bicycling and Calories Question 2 Answer Approximately how long could you live off a cereal bar containing 200 Calories? 30 min 1 h 2-3 h 5-6 h More than 6 hours Physics and Astronomy Outreach Program at the University of British Columbia

  8. Bicycling and Calories Question 2 Solution Approximately how long could you live off a cereal bar containing 200 Calories? 2000 kcal/day ~ 83 kcal/h 200 kcal / (83 kcal/h) = 2.4 hours Therefore you can live 2-3 hours off of a cereal bar. Physics and Astronomy Outreach Program at the University of British Columbia

  9. Bicycling and Calories Question 3 What needs more energy, your body or a refrigerator that consumes 1.2 kWh/day? Approximately same amount Refrigerator needs more energy Human body needs more energy Physics and Astronomy Outreach Program at the University of British Columbia

  10. Bicycling and Calories Question 3 Answer What needs more energy, your body or a refrigerator that consumes 1.2 kWh/day? Approximately same amount Refrigerator needs more energy Human body needs more energy Physics and Astronomy Outreach Program at the University of British Columbia

  11. Bicycling and Calories Question 3 Solution What needs more energy, your body or a refrigerator? Your body requires 2000 Calories/day or 2000 kcal/day. (2000 kcal/day)(4200 J/kcal) = 8.4 x 106 J/day (8.4 x 106 J/day)(1 day/86400 s) = 100 W A refrigerator requires 1.2 kWh/day (1.2 kWh/day)(3.6 x 106 J/kWh) = 4.3 x 106 J/day (4.3 x 106 J/day)(1 day/86400 s) = 50 W Physics and Astronomy Outreach Program at the University of British Columbia

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