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

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AP Physics 2

Thermal Physics

Multiple Choice www.njctl.org

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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 C Entropy is reduced during the process D The natural flow of heat will be from the warmer system to the colder system

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2 When one end of a cold metal spoon is placed upright in a cup of hot coffee, the other end eventually gets warmer. On the scale of the molecules of the spoon, which of the following is the primary explanation of this phenomenon? A Warmer molecules will rise to the top B The hot molecules produce thermal radiation that is then absorbed by the colder molecules. C Higher-energy molecules hit lower-energy molecules, 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

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3 It is outside 20 οC in Josh’s backyard. If her crabapple tree only blooms when the temperature is about 25 οC, what will the temperature need to be in Fahrenheit before they bloom? A 71 οF B 77 οF C 85 οF D 25 οF

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4 Rose doesn’t feel well, but her mom will only let her stay home from school if she has a fever. She knows that she needs to have a temperature that is at least 99.5 οF 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 99.5 οC B 27.5 οC C 37.5 οC D 38.5 οC

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5 If systems 2 and 3 are both at thermal equilibrium with system 1, which of the following must be true? A Systems 2 and 3 are in thermal equilibrium with each other B System 2 has a higher temperature than system 3 C System 3 has a higher temperature than system 2 D Systems 2 and 3 are not in thermal equilibrium with each

• ther

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6 Assuming that the coefficient of linear expansion of a metal bar is is the same from 0°C to 50°C, which of the following temperature changes will produce the largest percent increase in the length of a metal bar? (select 2 answers). A An increase in temperature from 10° C to 14° C B An increase in temperature from 30° C to 31° C C An increase in temperature from 293 K to 297 K D A decrease in temperature from 48° C to 40° C

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7 A metal cup is left outdoors in the hot sun. As the cup’s temperature increases, which of the following statements about the inner and outer circumferences of the cup is true? A The outer circumference will not change, but the inner circumference will decrease. B The outer circumference will increase, but the inner circumference will not change. C The outer circumference will increase, but the inner circumference will decrease. D Both the outer and the inner circumferences will increase

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8 A bimetal plate consists of two materials of different coefficients of thermal expansion. The coefficient of thermal expansion of the top part of the plate is less than the bottom part. If the temperature of the entire plate increases, what happens to the plate? A Expands B Contracts C Stays the same D Bends up

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9 A flat metal ring as shown increases in temperature over time. How will its shape change? (select 2 answers) A The inner radius will decrease B The outer radius will increase C The inner radius will increase D The outer radius will decrease

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10 At midnight, the temperature is 10 °C. At noon the next day, the temperature is 20°C. If a glass building was 413m tall at midnight, how many meters did it grow during the day? (The coefficient of linear thermal expansion for glass is approximately 8.5x10-6 (οC)-1) A 413 m B 0.7 m C 0.035 m D 0.0011 m

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11 A solid copper ball with a mass of 50g and a temperature of 30 degrees Celsius is placed on a sheet of ice at 0 οC, which then

• melts. If 50g of water at the same temperature were poured on the

ice, would it melt the same amount of ice as the copper ball? A The water would melt more ice B The water would melt less ice C The water would melt the same amount of ice D Neither would melt any ice

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12 Two metal bars are kept at the same temperature and are aligned with their nearer ends separated by a distance of 0.1m. Their far ends are clamped in place. One bar is made out of steel (α=10-5 (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 touch? A 10 οC B 100 οC C 1000 οC D 10000 οC

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13 The specific heat of a liquid is 1000 J/(kg•K). How much heat is needed to raise the temperature of 2 kg of this liquid from 10 οC to 20 οC? A 2,000 J B 10,000 J C 20,000 J D 40,000 J

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14 Approximately how much heat must be removed from 0.5 kg of 50 °C water to freeze it into 0 °C ice? [for water Lf = 334,000 J/kg and c = 4200 J/(kg•K) ] A 105 J B 105,000 J C 167,000 J D 272,000 J

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15 Which of the following is true about melting process? A The energy is required to increase the average kinetic energy of molecules B The energy is required to decrease the average kinetic energy of molecules C The energy is required to increase the potential energy between the molecules D No energy is required for this process it happens spontaneously

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16 A metal rod is placed so that it connects a heat source at 100°C and a heat sink at 10°C. During time t, an amount of heat Q is transferred from the source to the sink. if the metal rod is replaced by another made of the same material but of three times the length, how much heat will be transferred during the same amount

• f time t?

A 1/9 Q B 1/3 Q C Q D 3 Q

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17 When we touch a piece of metal and a piece of wood that are placed in the same room, the piece of metal feels much colder than the piece of wood. This happens because of the difference in: A Specific heat B Temperature C Thermal conductivity D Latent heat

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18 Given their coefficients of thermal conductivity, which of the following materials would best insulate a building? A Diamond (k= 2000 W/m•K) B Glass (k= 1 W/m•K) C Asbestos (k= 0.09 W/m•K) D Air (k=0.026 W/m•K)

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19 The state of an ideal gas was changed three times at three different temperatures. The diagram represents three different isothermal curves. Which of the following is true about the temperature of the gas? A T1 < T2 < T3 B T1 > T2 > T3 C T1 > T2 < T3 D T1 > T2 = T3

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20 The state of an ideal gas was changed three times in a way that the pressure stays the same. The graph represents three isobaric

• lines. Which of the following is true about the pressure of the gas?

A P1 > P2 > P3 B P1 > P2 < P3 C P1 < P2 < P3 D P1 = P2 > P3

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21 Kinetic Theory is based on an ideal gas model. The following statements about the ideal gas are true EXCEPT: A All molecules move with the same speed B The average molecular kinetic energy is directly proportional to the absolute temperature C All molecules make elastic collisions with each other and the walls of the container D The attractive force between the molecules can be ignored

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22 Helium gas is sealed in a container. The container is heated, causing the temperature to increase at a constant rate. Which of the following statements is NOT true? A The pressure of the gas increases at a constant rate B Temperature of the gas increases at a constant rate C The average kinetic energy of the gas particles increases at a constant rate D The average speed of the gas particles increases at a constant rate

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23 A cylindrical container is sealed by a circular lid. The pressure in the room surrounding the container is 1.0 × 105 N/m2. The pressure inside the container is 0.3 × 105 N/m2. The lid has radius 0.10 m and weight 100 N. What is the minimum force required to lift the lid

• ff of the container?

A 3.15 × 103 N B 2.20 × 103 N C 2.30 × 103 N D 1.04 × 103 N

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24 A gas with volume V, pressure P, and temperature T is trapped inside a cylindrical container with a moveable piston. If the temperature of a trapped gas is quadrupled while the volume is doubled, what will be the new pressure? A P B 1.5 P C 2 P D 3 P

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25 A cylindrical container of volume V holds 3 moles of Neon gas with pressure P and temperature T. If the gas is heated to a temperature of 2T and volume is kept constant, how many moles

• f gas are there in the container?

A 3 moles B 1.5 moles C 1 mole D 0 moles

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26 A box contains a volume V of air with a pressure P and temperature T. If the box is never opened and no air can escape. If the temperature in the room is increased to 2T, what will be the new pressure in the box? A 1/2 P B P C 2 P D 4 P

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27 A sample of ideal gas has an internal energy U and is then compressed to one-half of its original volume while the temperature stays the same. What is the new internal energy of the ideal gas in terms of U? A U B 1/2 U C 1/4 U D 2 U

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28 An ideal gas with an internal energy U initially at 0 ̊C is heated to 273 ̊C. What is the new internal energy in terms of U? A U B 1/2 U C 1/4 U D 2 U

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29 Three containers are filled with 1 kg of each: water, ice, and water vapor at the same temperature T = 0°C. Which of the following is true about the internal energy of the substances? A U water > U ice > U vapor B U water = U ice = U vapor C U water < U ice < U vapor D U ice < U water < U vapor

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30 An ideal gas is initially in state A, as shown in the PV diagram (right). The gas undergoes a transition from state A by the three different processes shown, where process III is isothermal. Which

• f the following processes shows positive work being done on the

gas? A I only B III only C I and II only D I, II and III

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31 An ideal gas is initially in state A, as shown in the PV diagram (right). The gas undergoes a transition from state A by the three different processes shown, where process III is isothermal. In which process is energy added to the gas? A I only B III only C I and II only D IIand III only

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32 A sample of an ideal gas can be taken from state A to state B through one of two processes, as shown in the graph of pressure P versus volume V (right). Which of the following will be the same for both processes? A The average kinetic energy of the gas B The temperature of the gas at the end of the process C The thermal energy transferred to the gas by heating D The work done on the gas

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33 Identical samples of gas initially have pressure 3P and volume 2V. The final temperature is equal to the initial temperature for which of the processes? (select 2 answers) A A B B C C D D

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34 Referring to the P-V diagram (right), how much work is done by the gas as it cycles once along the path A → B → C → A? A PV B 1/2 PV C 2 PV D 4 PV

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35 Which of the following lines on the graph above shows an adiabatic process? (Select two answers) A A - B B B - C C C - D D D - A

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36 Which of the following lines on the graph above shows an isothermal process? (Select two answers) A A - B B B - C C C - D D D - A

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37 The state of an ideal gas is changed isothermally from position 1 to position 2 is shown right. What is the change in the internal energy

• f the gas during this process?

A ΔU = W B ΔU = Q C ΔU > 0 D ΔU = 0

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38 An ideal gas is taken from state 1 to state 2 and then to state 3. If the process 1-2 is adiabatic and 2-3 is isothermal, what is a true statement about the change in temperature and heat transferred during 1-2? A ΔT > 0, Q > 0 B ΔT < 0, Q = 0 C ΔT = 0, Q = 0 D ΔT = 0, Q < 0

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39 Why does the isothermal curve look the way it does? A PV= nRT, so the PV graph is comparable to the graph of y=x B PV= nRT, so the PV graph is comparable to the graph of y=x2 C PV= nRT, so the PV graph is comparable to the graph of y= 1/x D PV= nRT, so the PV graph is comparable to the graph of y=x3

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40 Which of the following is a characteristic of an adiabatic process? A ΔU = 0 B W = 0 C Q = 0 D ΔV = 0

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41 A container is filled with Helium gas to a pressure P at a temperature T. Oxygen, which has atoms that are 4 times more massive than those of helium, is then added to the container until the new pressure in the container is 2P at the same temperature T. The ratio of the average speed of the helium atoms to the average speed of the Oxygen atoms is A 4 to 1 B 2 to 1 C √2 to 1 D 1 to 1

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42 A container is filled with Helium gas to a pressure P at a temperature T. Oxygen, which has atoms that are 4 times more massive than those of helium, is then added to the container until the new pressure in the container is 2P at the same temperature T. The ratio of the number of helium atoms to oxygen atoms in the container is A 5 to 1 B 6 to 1 C 16 to 1 D 1 to 1

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43 A sealed container of air is kept at a constant temperature. What will happen to the speed/average kinetic energy of the molecules

• f air in the container as time passes?

A The molecules will obey the second law of thermodynamics. Eventually, there will be no deviations in the speed of kinetic energy of the air molecules whatsoever. B Some molecules will speed up and others will slow down, but the average speed and kinetic energy will be constant C The molecules will slow down, decreasing their average kinetic energy D There will be no change

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44 Two boxes of equal volume each contain the same quantity of an ideal gas. The first box is much warmer than the second box. Which of the following statements MUST be true? (select 2 answers) A The pressure in the first box is greater than the pressure in the second box B There are more molecules in the first box than in the second box C The boxes contain different types of gasses D The molecules in the first box have a higher average kinetic energy than those in the second box

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45 During a thermodynamic process, 2,000 J of heat are removed from a gas while 600 J of work is done by the gas. What is the change in internal energy of the gas? A +2,600 J B 0 C -1,400 J D -2,600 J

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46 The internal energy of a sample of confined helium gas is increased by 300 J. If the net amount of work done on the sample by its surroundings was 240 J, how much heat was transferred between the gas and its environment? A 60 J absorbed B 540 J absorbed C 60 J dissipated D 540 J dissipated

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47 Ice is placed in an empty container in a room where the air temperature is 20°C and allow to melt. While the ice is melting the temperature of the water is… A less than 0°C B 0°C C room temperature D greater than 0°C but less than room temperature

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48 A gas undergoes an expansion in which 300 J of energy is added to the gas by heating. The internal energy of the gas changes from 600 J to 700 J. The work done by the gas is: A 1,300 J B 900 J C 200 J D 100 J

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49 Convection can occur in which of the following substances? (Select two answers) A Solids B Liquids C Bose-Einstein Condensate D Gasses

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50 If the absolute temperature of a radiating object is doubled, by what factor does the rate of energy emission change? A 2 B 4 C 16 D 32

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51 The product of pressure and volume is expressed most commonly in which of the following units: A Joules B Pascal∙meters2 C Farads D Pascals

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52 A gas trapped in a container with a movable piston undergoes an adiabatic process. During this process, the gas does about 1025 joules of work. Which of the following statements are true? (select 2 answers) A The internal energy of the system increases by 1025 J B The temperature of the gas increases C The temperature of the gas decreases D The heat transferred in or out of the system is zero

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53 At higher altitudes, the air is colder. Why does this happen? A There are fewer air molecules at higher altitudes, so are less collisions between molecules and the air loses energy quickly B As a quantity of air moves to a higher altitude, it experiences a decrease in pressure. This causes the air to expand. Since no heat is being added, the internal energy of the air drops, and therefore its temperature drops. C There are fewer people living in higher altitudes, at much of the warmth of our planet comes from human emissions like body heat and greenhouse gasses that are heavily concentrated in more populated areas. D It is not colder in higher altitudes.

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54 Which statement must be true regarding two systems of unequal temperature that come in contact with one another? A The final temperature will be the average of the two systems’ temperatures B The final temperature will be greater than that of the warmer system C There will be a decrease in total energy D The total amount of thermal energy will be constant

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55 An engine has an efficiency of 20% and produces 2000 J of mechanical work during one cycle. How much energy is transferred

• ut of the engine by heating the environment during one cycle?

A 100 J B 2000 J C 8000 J D 10000 J

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56 A Carnot engine takes 2000 J of heat from a reservoir at 200 οC, does some work, and releases some heat into a second reservoir at 20 οC. What is the efficiency of the engine? A 4% B 10% C 38% D 90%

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57 A Carnot engine takes 2000 J of heat from a reservoir at 200 οC, does some work, and releases some heat into a second reservoir at 20 οC. How much work is done by the engine? A 80 J B 200 J C 1800 J D 760 J

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58 A Carnot engine takes 2000 J of heat from a reservoir at 200 οC, does some work, and releases some heat into a second reservoir at 20 οC. How much heat is discarded by the engine? A 1340 J B 1920 J C 1800 J D 200 J