Homework 1 egee

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Pennsylvania State University *

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101H

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Aerospace Engineering

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Apr 3, 2024

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docx

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2

Uploaded by BarristerSnowManatee27

Homework 1 EGEE 101H, Homework #1 – Unit Conversions January 22, 2014 Due on Thursday, January 29 by electronic submission to the HW1 drop box, by 11:59 p.m. Submit, MS Excel, MS Word, or pdf. Scanned copies of handwritten pages are not acceptable. Each question is worth 12.5 pts. 1. Calculate the work done (in Joules) by a 75-kilogram woman to climb to the top of Mount Everest (29,028 feet)? (Conversion factors you need to solve this problem: 1 meter= 3.28 feet, Gravitational Acceleration =9.8 m/sec/sec. Note that work = force x distance, and force = mass x gravitational acceleration) 29,028ft*1m/3.28ft=8850m F=ma (75kg)(9.8m/s^2)=F=735mkg/s^2 W=Fd 735mkg/s^2 /8850m=w w=6,504,750J 2. What is the energy equivalent of the work done in Question 1 in slices of pizza? (Conversion factors you need to solve this problem: Energy content of one slice of pizza = 290 Calories and 1 Calorie = 4,184 Joules) Comment briefly on why your answer (which is thermodynamically correct) is not really the right answer. 6,504,750J/1* 1cal/4184J*1 pizza/290 cal= 5.36 pizzas This answer cannot be the actual answer because there are human limitations for climbing Everest. Plus this “5.36 Pizzas” is assuming that us humans are robots and that we are 100% efficient in eating these foods. Plus we have to convert this energy into mechanical energy and this will also take some conversion and lose some heat. As a result, the 5.36 pizzas are completely theoretical, and thus cannot be actually the right
answer. 3. Annual per capita energy consumption in the U.S. is approximately 350 million Btu. Calculate how many pounds of coal would have the equivalent amount of energy (The value of a typical coal is 13,000 Btu/lb). 350million btu/1*1 lb coal/13,000 BTU= 26,923.08 lbs of coal 4. The wattage of a typical color TV is 300 (i.e., it uses 300 watts of electric power). If one kilowatt-hour of electricity costs 6 cents, how much does it cost to watch TV for 3 hours? (1 kilowatt = 1000 watts). 3 hours*300 watts/1hr*1 kw/1000w*6 cents/1 kw=5.4 cents 5. The speed of light is approximately 300,000 kilometers/second, and the distance from the sun to the earth is approximately 150,000,000 kilometers. How long (in minutes) does the solar radiation take to reach the earth? 150,000,000 km * 1/300,000km * 1min/60s = 8.33 minutes 6. An elevator needs a power of 10 kW to run smoothly. Calculate its power in units of horsepower. 10kw/1 * 1000 w / 1kw * 1hp/746= 13.40 hp 7. A typical adult in U.S. converts 2000 Calories of food energy per day. Calculate the average metabolic power of an adult, assuming that the energy is converted evenly throughout the day (24 hours). (You know that this assumption is not true. One converts, for example, much less energy by sleeping than by walking or running). 2000cal/day*4184j/1cal*1day/24 hours*1 hr/60min* 1 min/ 60s 96.85 watts 8. Calculate how many kilograms of carbon dioxide (CO2) are produced when one kilogram of natural gas (i.e., methane, CH4) is burnt completely to carbon dioxide and water. 1 kg CH4=1000g CH4*1 mol CH4/16g CH4* 1 mol CO2/1 mol CH4*44 g CO2/1 mol Co2 2750g/1000g = 2.75 kg
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