PHYS/ENVS 3070 Homework Assignment #2: Problem #1: Below is the nutritional information about a Snicker's Candy Bar. What is the energy content of this product in the following units? a) Joules; b) British Thermal Units; c) Calories; d) kiloWatt-hours; e) foot-pounds Nutrition Facts Serving Size: (100 grams) Amount Per Serving Calories: 467 % Daily Value* Total Fat 19g 29% Saturated Fat 7g 36% Cholesterol 14mg 4% Sodium 228mg 9% Total Carboydrates 65g 21% Dietary Fiber 3g ~ Sugars 50g ~ Protein 9g 18% Vitamin A 2% Vitamin C 0% Iron 6% Calcium 10% *Percent Daily Values are based on a 2000 calorie diet. Your daily values may be higher or lower depending on your calorie needsProblem #2: It has been estimated that a person can perform continuous manual labor at a power of 60 Watts for an 8 hour working day. a) How many gallons of crude oil contain the energy equivalent of the useful physical labor a person can perform in a 5 day work week? b) How many pounds of coal contain the energy equivalent of the useful physical labor a person can perform in a 5 day work week? c) How many cubic feet of natural gas contains the energy equivalent of the useful physical labor a person can perform in a 5 day work week? Problem #3: A bacterial colony starts growing in a jar at 11:00 am. The size of the colony doubles every minute, and the jar is just full at 12:00 noon. How many minutes past 11:00 am was the jar 1/16 full? Problem #4: Identify each of the following units as being either a unit of Energy or a unit of Power or Neither. a) BTU / hour b) horsepower c) kiloWatt - hour d) Joule / second e) horsepower / second f) BTU / Watt Problem #5: Later this semester we will learn that we could meet all of the energy needs in the United States if we covered 0.16% of the entire country (including all states) with very efficient solar panels. a) Calculate how large an area in square miles is the equivalent of this 0.16%.b) Relate this area to the size of the state of Colorado? c) Convert the area in square miles into square meters. d) Ignoring certain practical issues, what is a reasonable estimate for the required cost of solar panels (per square meter) to consider such an option? Give a basis for your estimate. Problem #6: I decide to connect my stationary bicycle to my water heater. Assume that I generate 100 Watts of power, and that my device is 50% efficiency at converting this energy to heat in the water. Assuming there is no cooling of the water due to poor insulation, how many hours must I cycle to increase the temperature of my 50 gallon water tank by 30 degrees
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