# 3. 15.2 The First Law of Thermodynamics and Some Simple Processes – College Phys

3. 15.2 The First Law of Thermodynamics and Some Simple Processes – College Physics – OpenStax CNX An aluminum block of mass 8.4 kg is originally at a temperature of 21°C and 1 atm. It is then heated to a temperature of 56°C without any change in pressure. The specific heat of aluminum is 900 J/(kg · °C), its density is 2.70 103 kg/m3, and the coefficient of linear expansion is 24 ✕ 10^−6/°C.(a) Determine the work done by the aluminum block. J(b) How much heat energy is transferred during this process? J(c) What is the increase in internal energy of the system? JReading: 1.15.2 The First Law of Thermodynamics and Some Simple Processes – College Physics – OpenStax CNXSuppose a woman does 963 J of work and dissipates 8,154 J of heat in the process.(a) What is the decrease in her internal energy, assuming no change in temperature or consumption of food? (That is, there is no other energy transfer.) kcal(b) What is her efficiency? %2. 15.2 The First Law of Thermodynamics and Some Simple Processes – College Physics – OpenStax CNX (a) How long will the energy in a 117 kcal cup of yogurt last in a woman doing work at the rate of 135 W with an efficiency of 20% (such as in leisurely climbing stairs)? min(b) Does the time found in part (a) imply that it is easy to consume more food calories in one day than you can reasonably expect to work off with an hour of exercise?YesNo 4. 15.3 Introduction to the Second Law of Thermodynamics: Heat Engines and Their Efficiency – College Physics – OpenStax CNX The engine of a large ship does 1.67 1010 J of work with an efficiency of 7.20%.(a) How much waste heat is produced? J(b) How many barrels of fuel are consumed if each barrel produces 6.00 109 J of heat when burned? barrels 5.15.4 Carnot’s Perfect Heat Engine: The Second Law of Thermodynamics Restated – College Physics – OpenStax CNX Determine the efficiency of a Carnot engine if the work it does is 7.77 times less than the heat that flows into the system. %.6.15.6 Entropy and the Second Law of Thermodynamics: Disorder and the Unavailability of Energy – College Physics – OpenStax CNX When 1.62 105 J of heat enters a cherry pie initially at 20.0°C, its entropy increases by 482 J/K. What is its final temperature? °C .7. 15.6 Entropy and the Second Law of Thermodynamics: Disorder and the Unavailability of Energy – College Physics – OpenStax CNX (a) During a process, the increase in entropy of a system is 3538 J/K, and the energy that becomes unavailable for doing work is zero. Which of the following statements is correct?The process is reversible because the zero energy unavailable for work increases the entropy of the universe.The process is irreversible because the zero energy unavailable for work makes ΔSuniverse = 0. The process is irreversible because the zero energy unavailable for work increases the entropy of the universe.The process is reversible because the zero energy unavailable for work makes ΔSuniverse = 0.(b) By how much does the entropy of the surroundings change? J/K