Exam 4 -- PHYS 101. Name: Class: Date: Multiple Choice Identify the choice that best completes the statement or answers the question.

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1 Name: Class: Date: Exam 4 -- PHYS 101 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. A steel tape measure is marked such that it gives accurate measurements at room temperature. You place the tape measure in a very cold place and measure the length of a bar which you know to be 1 meter in length. What length will the cold tape measure show? a. length = 1 meter c. length > 1 meter b. length < 1 meter d. Not enough information 2. You want to take apart a couple of steel parts held together by brass screws, but the parts are stuck. What should you do to remove the screws? (The coefficient of linear expansion for steel is C -1. The coefficient for brass is C -1.) a. heat the parts c. Not enough information given b. cool the parts 3. Which of these is the Kelvin temperature scale not based upon? a. freezing point of water d. temperature of the cosmic background b. heat of vaporization of water e. all of the above c. boiling point of water 4. Which is the smallest unit of temperature: one degree Kelvin, Celsius, or Fahrenheit? a. Celsius c. Kelvin & Celsius b. Kelvin d. Fahrenheit 5. You heat a bimetallic strip that is made of brass on one side and steel on the other side. As you heat it, the strip will bend towards which side? (The coefficient of linear expansion for steel is C -1. The coefficient for brass is C -1.) a. the brass side c. the strip will not bend b. the steel side d. don t know 6. An atomic ideal gas occupies a volume of 0.01 m 3 at 30 C and a pressure of Pa. How many atoms are present in the gas? (universal gas constant=8.314 J/(mol K); Boltzmann s constant = J/K; Avogadro s number is ) a. 4.0 moles c. 0.4 atoms b atoms d atoms 7. A containter of atomic gas is present in a volume of 0.02 m 3, with a temperature of 20 C, and at a pressure of 1 atmosphere. If the pressure drops to atmosphere, what is the temperature? (ideal gas constant = J/mol K; 1 atm = Pa) a. 0 C c. 2.7 K b K d. 3 mk 1

2 Name: 8. Two identical cylinders at the same temperature contain the same gas. If container A has 4 times as much gas as container B, which has the highest pressure? a. A c. they have the same pressure b. B d. not enough information given 9. Neon has a molar mass of kg/mol. Helium has a molar mass of kg/mol. In one mole, which has the greater number of atoms? a. Neon c. both the same b. Helium 10. A steel bar is 10 meters long. It is heated from 100 C to 1000 C. What is the new length of the steel bar? (The coefficient of linear expansion for steel is C -1.) For this problem, ignore the proper use of significant figures. a m c. 10 cm b m d. 0.1 m 11. The specific heat of aluminum is 900 J/kg C. The specific heat of glass is 837 J/kg C. If two pieces of glass and aluminum, each with the same mass, are placed in an oven. For which of these will the temperature rise more quickly? a. aluminum c. temperature of both will increase at same rate b. glass d. not enough information given 12. Water falls from 50 meters. Assume all gravitational potential energy is converted to thermal energy. What is the change in temperature of the water? The specific heat of water is 4186 J/kg C. a. 0.1 C c. 1 C b C d. not enough information given 13. You place a mass of copper at -10 C into a container with 100 g of steam at 100 C. The system reaches an equilibrium temperature of 45 C. What is the mass of the copper? (for water: latent heat of vaporization= J/kg, latent heat of fusion= J/kg, and specific heat=4186 J/kg C. For copper, the specific heat is 387 J/kg C.) a. 10 kg c. 1 kg b. 3 kg d. 10,000 kg 14. Does one transer heat into a substance (Q>0) or take heat away from a substance (Q<0) in order to convert it from a vapor to a liquid? a. Q<0 c. not enough information b. Q>0 d. neither, Q=0 2

3 Name: 15. Convection is the transfer of heat caused by a. contact between two objects c. the conversion of work to heat b. the transfer of radiation d. the motion of a substance 16. Water has a higher specific heat than sand. Therefore, in the afternoon, breezes blow a. from the beach to the ocean c. either way, makes no difference b. from the ocean to the beach 17. You put 1 kg of ice at 0 C with 1 kg of water at 50 C. What is the final temperature of the water? (For water: latent heat of vaporization= J/kg, latent heat of fusion= J/kg, and specific heat=4186 J/kg C.) a. 25 C c. 0 C b. 75 C d. 50 C 18. A special type of star has a temperature of 100,000 K and a radius of 10 3 m. The star is a perfect blackbody absorber. What power is radiated by the star in the form of radiation? (The Stefan-Boltzmann constant is W/m 2 K 4 ) a W c. 0 W b. 6 W d. 70,000 W 19. How much heat is required to raise the temperature of 100 g of ice from -20 C to 50 C? (For water: latent heat of vaporization= J/kg, latent heat of fusion= J/kg, and specific heat=4186 J/kg C.) a J c J b J d J 20. Zero degrees Celsius is equivalent to which of these temperatures: a. 273 K c K b. 20 F d. -32 F 21. In which of these processes is the internal energy of the gas equal to the work done on the gas? a. adiabatic d. isovolumetric b. isothermal e. isochroic c. isobaric 3

4 Name: 22. In this figure, what is the work done on the gas when it follows the path ab (beginning at a and ending at b)? a c. -12,000 J b. 12,000 J d. -10,000 J 23. In the figure for problem 22, what is the heat transferred to the gas for the cyclic path ABCA? a. 6,000 J c. -6,000 J b. 12,000 J d. 6 J 24. In a heat engine, 10,000 J of heat is absorbed by the steam from the coal boiler. This steam powers a turbine with 8,000 J of work. Then, 2,000 J of heat is dispersed in a cooling tower. What is the efficiency of this heat engine? a. 20% c. 80% b. 160% d. 25% 25. Which of these is not a step in the 4-stroke internal combustion engine? a. power c. exhaust b. ignition d. intake 26. The second law of thermodynamics says which of these can never be zero? a. entropy c. work b. heat from the hot reservoir d. heat to the cold reservoir 4

5 Name: 27. A movable piston has a mass of 8.00 kg and an area of 9.50 cm 2. Inside the piston, 0.1 moles of an ideal gas experience a temperature change from 30 C to 100 C while the piston moves (without friction). How much work is done on the gas? (universal gas constant=8.314 J/(mol K); Boltzmann s constant = J/K; Stefan-Boltzmann constant= W/(m 2 K 4 )) a J c J b. 60 J d. -60 J 28. Gas in a container is at a pressure of 1000 Pa and a volume of 4 m 3. How much work is done on the gas if it expands at constant pressure to three times its original volume? a. 8,000 J c. -8,000 J b. -12,000 J d. 4,000 J 29. An ideal, monatomic gas undergoes a thermal process where no heat is transferred to the gas. The inital pressure is 1000 Pa, and the initial volume is 0.1 m 3. The final volume is 0.2 m 3. What is the final pressure? (For a monatomic gas, Cp= 5 2 R and Cv= 3 2 R.) a. 300 Pa c. 700 Pa b. 100 Pa d. 500 Pa 30. You are using version A of this test. Please bubble A and write Version A on your scantron. a. A c. C b. B d. D 5

6 Exam 4 -- PHYS 101 Answer Section MULTIPLE CHOICE 1. ANS: C PTS: 1 2. ANS: B PTS: 1 3. ANS: E PTS: 1 4. ANS: D PTS: 1 5. ANS: B PTS: 1 6. ANS: D PTS: 1 7. ANS: D PTS: 1 8. ANS: A PTS: 1 9. ANS: C PTS: ANS: B PTS: ANS: B PTS: ANS: A PTS: ANS: A PTS: ANS: A PTS: ANS: D PTS: ANS: B PTS: ANS: C PTS: ANS: C PTS: ANS: D PTS: ANS: A PTS: ANS: A PTS: ANS: D PTS: ANS: A PTS: ANS: C PTS: ANS: B PTS: ANS: D PTS: ANS: D PTS: ANS: C PTS: ANS: A PTS: ANS: A PTS: 1 1