AP Physics 2 C Entropy is reduced during the process Thermal - PDF document

Slide 1 / 59 Slide 2 / 59 1 Which of the following is NOT true when two systems with unequal temperatures come into contact with one another? A Heat will flow until thermal equilibrium is reached B No net heat flow occurs once thermal equilibrium is reached AP Physics 2 C Entropy is reduced during the process Thermal Physics D The natural flow of heat will be from the warmer system to the colder system Multiple Choice www.njctl.org Slide 3 / 59 Slide 4 / 59 2 When one end of a cold metal spoon is placed upright in a cup of 3 It is outside 20 ο C in Josh’s backyard. If her crabapple tree only hot coffee, the other end eventually gets warmer. On the scale of blooms when the temperature is about 25 ο C, what will the the molecules of the spoon, which of the following is the primary temperature need to be in Fahrenheit before they bloom? explanation of this phenomenon? A 71 ο F A Warmer molecules will rise to the top B 77 ο F B The hot molecules produce thermal radiation that is then absorbed by the colder molecules. C 85 ο F C Higher-energy molecules hit lower-energy molecules, D 25 ο F increasing their speed and thus their temperature D Hotter areas have more molecules, which will flow upwards from areas of high concentration to low concentration Slide 5 / 59 Slide 6 / 59 4 Rose doesn’t feel well, but her mom will only let her stay home 5 If systems 2 and 3 are both at thermal equilibrium with system 1, from school if she has a fever. She knows that she needs to have a which of the following must be true? temperature that is at least 99.5 ο F before she is allowed to stay home, but her thermometer works in Celsius instead of Fahrenheit. What temperature does the thermometer need to be? A Systems 2 and 3 are in thermal equilibrium with each other B System 2 has a higher temperature than system 3 A 99.5 ο C C System 3 has a higher temperature than system 2 B 27.5 ο C D Systems 2 and 3 are not in thermal equilibrium with each C 37.5 ο C other D 38.5 ο C

Slide 7 / 59 Slide 8 / 59 6 Assuming that the coefficient of linear expansion of a metal bar is 7 A metal cup is left outdoors in the hot sun. As the cup’s is the same from 0°C to 50°C, which of the following temperature temperature increases, which of the following statements about the changes will produce the largest percent increase in the length of a inner and outer circumferences of the cup is true? metal bar? (select 2 answers). A The outer circumference will not change, but the inner circumference will decrease. A An increase in temperature from 10° C to 14° C B The outer circumference will increase, but the inner circumference will not change. B An increase in temperature from 30° C to 31° C C The outer circumference will increase, but the inner C An increase in temperature from 293 K to 297 K circumference will decrease. D A decrease in temperature from 48° C to 40° C D Both the outer and the inner circumferences will increase Slide 9 / 59 Slide 10 / 59 8 A bimetal plate consists of two materials of different coefficients of 9 A flat metal ring as shown increases in temperature over time. How thermal expansion. The coefficient of thermal expansion of the top will its shape change? (select 2 answers) part of the plate is less than the bottom part. If the temperature of the entire plate increases, what happens to the plate? A The inner radius will decrease A Expands B The outer radius will increase B Contracts C The inner radius will increase C Stays the same D The outer radius will decrease D Bends up Slide 11 / 59 Slide 12 / 59 10 At midnight, the temperature is 10 °C. At noon the next day, the 11 A solid copper ball with a mass of 50g and a temperature of 30 temperature is 20°C. If a glass building was 413m tall at midnight, degrees Celsius is placed on a sheet of ice at 0 ο C, which then how many meters did it grow during the day? (The coefficient of melts. If 50g of water at the same temperature were poured on the linear thermal expansion for glass is approximately 8.5x10 -6 ( ο C) -1 ) ice, would it melt the same amount of ice as the copper ball? A 413 m A The water would melt more ice B 0.7 m B The water would melt less ice C 0.035 m C The water would melt the same amount of ice D 0.0011 m D Neither would melt any ice

Slide 13 / 59 Slide 14 / 59 12 Two metal bars are kept at the same temperature and are aligned 13 The specific heat of a liquid is 1000 J/(kg•K). How much heat is with their nearer ends separated by a distance of 0.1m. Their far needed to raise the temperature of 2 kg of this liquid from 10 ο C to ends are clamped in place. One bar is made out of steel (α=10 -5 20 ο C? (C) -1 ). The other is made out of iron (α=1.2x10 -5 (C) -1 ). If the steel bar is initially 4 m long and the iron bar is initially 5 m long, how much must the temperature of the bars be changed to get them to A 2,000 J touch? B 10,000 J A 10 ο C C 20,000 J B 100 ο C D 40,000 J C 1000 ο C D 10000 ο C Slide 15 / 59 Slide 16 / 59 14 Approximately how much heat must be removed from 0.5 kg of 50 15 Which of the following is true about melting process? °C water to freeze it into 0 °C ice? [for water Lf = 334,000 J/kg and c = 4200 J/(kg•K) ] A The energy is required to increase the average kinetic energy of molecules A 105 J B The energy is required to decrease the average kinetic B 105,000 J energy of molecules C 167,000 J C The energy is required to increase the potential energy between the molecules D 272,000 J D No energy is required for this process it happens spontaneously Slide 17 / 59 Slide 18 / 59 16 A metal rod is placed so that it connects a heat source at 100°C 17 When we touch a piece of metal and a piece of wood that are and a heat sink at 10°C. During time t, an amount of heat Q is placed in the same room, the piece of metal feels much colder than transferred from the source to the sink. if the metal rod is replaced the piece of wood. This happens because of the difference in: by another made of the same material but of three times the length, how much heat will be transferred during the same amount of time t? A Specific heat B Temperature A 1/9 Q C Thermal conductivity B 1/3 Q D Latent heat C Q D 3 Q

Slide 19 / 59 Slide 20 / 59 18 Given their coefficients of thermal conductivity, which of the 19 The state of an ideal gas was changed three times at three following materials would best insulate a building? different temperatures. The diagram represents three different isothermal curves. Which of the following is true about the temperature of the gas? A Diamond (k= 2000 W/m•K) B Glass (k= 1 W/m•K) A T1 < T2 < T3 C Asbestos (k= 0.09 W/m•K) B T1 > T2 > T3 C T1 > T2 < T3 D Air (k=0.026 W/m•K) D T1 > T2 = T3 Slide 21 / 59 Slide 22 / 59 20 The state of an ideal gas was changed three times in a way that 21 Kinetic Theory is based on an ideal gas model. The following the pressure stays the same. The graph represents three isobaric statements about the ideal gas are true EXCEPT: lines. Which of the following is true about the pressure of the gas? A All molecules move with the same speed A P1 > P2 > P3 B The average molecular kinetic energy is directly proportional B P1 > P2 < P3 to the absolute temperature C P1 < P2 < P3 C All molecules make elastic collisions with each other and the walls of the container D P1 = P2 > P3 D The attractive force between the molecules can be ignored Slide 23 / 59 Slide 24 / 59 22 Helium gas is sealed in a container. The container is heated, 23 A cylindrical container is sealed by a circular lid. The pressure in causing the temperature to increase at a constant rate. Which of the room surrounding the container is 1.0 × 10 5 N/m 2 . The pressure the following statements is NOT true? inside the container is 0.3 × 10 5 N/m 2 . The lid has radius 0.10 m and weight 100 N. What is the minimum force required to lift the lid off of the container? A The pressure of the gas increases at a constant rate B Temperature of the gas increases at a constant rate A 3.15 × 10 3 N B 2.20 × 10 3 N C The average kinetic energy of the gas particles increases at a constant rate C 2.30 × 10 3 N D The average speed of the gas particles increases at a constant rate D 1.04 × 10 3 N