Physics I Exam 4

about what percentage of the heat produced by burning gasoline is turned into useful work by a typical automobile A. 20% B. 50% C. 80% D. 90% E. nearly 100%

A

as heat is added to water, is it possible for the temperature measured by a thermometer in the water to remain constant A. yes, the water could be changing phase B. no, adding heat will always change the temperature C. maybe; it depends on the rate at which heat is added D. maybe; it depends on the initial water temperature

A

for objects at thermal equilibrium, which of the following is true? A. each is at the same temperature B. each has the same internal energy C. each has the same heat D. all of the above E. none of the above

A

in a mixture of the gases oxygen and helium, which statement is valid A. the helium atoms will be moving faster than the oxygen molecules, on average B. both will be moving at the same speed C. the oxygen molecules will, on average, be moving more rapidly than the helium atoms D. the kinetic energy of helium atoms will exceed that of oxygen molecules E. none of the above

A

two equal mass liquids, initially at the same temperature, are heated for the same time over the same stove. You measure the temperatures and find that one liquid has a higher temperature than the other. Which liquid has the higher specific heat A. the cooler one B. the hotter one C. both are the same

A

when using the ideal gas law, which of the following rules must be obeyed A. always use temperature in kelvins and absolute pressure B. always use volume in m^3 and temperature in kelvins C. always use gauge pressure and temperature in degrees celsius D. always use gauge pressure and temperature in kelvins E. always use volume in m^3 and gauge pressure

A

which of the following possibilities could increase the efficiency of a heat engine or an internal combustion engine? A. increase the temperature of the hot part of the system and reduce the temperature of the exhaust B. increase the temperatures of both the hot part and the exhaust of the system by the same amount C. decrease the temperatures of both the hot part and the exhaust part of the system by the same amount D. decrease the temperature of the hot part and increase the temperature of the exhaust part by the same amount E. none of the above; only redesigning the engine or using better gas could improve the engine's efficiency

A, C

an ideal gas undergoes an adiabatic expansion, a process in which no heat flows into or out of the gas. As a result, A. the temperature of the gas remains constant and the pressure decreases B. both the temperature and pressure of the gas decrease C. the temperature of the gas decreases and the pressure increases D. both the temperature and volume of the gas increase E. both the temperature and the pressure of the gas increase

B

one mole of an ideal gas in a sealed rigid container is initially at a temperature of 100 C. The temperature is then increased to 200 C. The pressure in the gas A. remains constant B. increases by about 25% C. doubles D. triples

B

when an ideal gas is warmed from 20 C to 40 C, the gas's temperature T that appears in the ideal gas law increases by a factor A. of 2 B. of 1.07 C. that depends on the temperature scale you use

B

which statement is true regarding the entropy change of an ice cube that melts A. since melting occurs at the melting point temperature there is no temperature change so there is no entropy change B. entropy increases C. entropy decreases

B

Two beaks contain ice and water at equilibrium. Beaker A has two ice cubes; beaker B has fifteen ice cubes. Which beaker is the coldest, or are they equal temperature? A. beaker A B. beaker B C. equal

C

a steel plate has a hole in it with a diameter of exactly 1.0 cm when the plate is at a temperature of 20 C. A steel ring has an inner diameter of exactly 1.0 cm at 20 C. Both the plate and the ring are heated to 100 C. Which statement is true? A. the hole in the plate gets smaller, and the opening in the ring gets larger B. the opening in the ring gets larger, but we need the relative size of the plate and the hole to know what happens to the hole C. the hole in the plate and the opening in the ring get larger D. the hole in the plate and the opening in the ring get smaller E. the hole in the plate gets larger, and the opening in the ring gets smaller

C

an ideal gas is in a sealed rigid container. The average kinetic energy of the gas molecules depends most on A. the size of the container B. the number of molecules in the container C. the temperature of the gas D. the mass of the molecules

C

an ideal gas undergoes an isobaric compression and then an isovolumetric process that brings it back to its initial temperature. Had the gas undergone one isothermal process instead, A. the work done on the gas would be the same B. the work done on the gas would be less C. the work done on the gas would be greater D. need to know the temperature of the isothermal process

C

heat is A. a fluid called caloric B. a measure of the average kinetic energy of atoms C. the amount of energy transferred between objects as a result of a difference in temperature D. an invisible, odorless, weightless substance E. the total kinetic energy of an ideal gas

C

rod A has twice the diameter of rod B, but both are made of iron and have the same initial length. Both rods are now subjected to the same change in temperature (but remain solid). How would the change in the rods' lengths compare? A. A > B B. B > A C. A = B D. need to know if the rods were heated or cooled

C

ten grams of water is added to ten grams of ice in an insulated container. Will all of the ice melt? A. Yes B. No C. more information is needed

C

the rms speed of the molecules of an ideal gas A. is the same as the most probable speed of the molecules B. is always equal to sqrt(2) times the maximum molecular speed C. will increase as the temperature of a gas increases D. all of the above

C

two identical bottles at the same temperature contain the same gas. If bottle B has twice the volume and contains half the number of moles of gas as bottle A, how does the pressure in B compare with the pressure in A? A. PB = 0.5PA B. PB = 2PA C. PB = 0.25PA D. PB = 4PA E. PB = PA

C

when you put an ice cube in a glass of warm tea, which of the following happens? A. cold flows from the ice cube into the tea B. cold flows from he ice cube into the tea and heat flows from the tea into the ice cube C. heat flows from the tea into the ice cube D. neither heat nor cold flows. Only temperature flows between the ice and the tea

C

which is possible: converting (i) 100 J of work entirely into 100 J of heat, (ii) 100 J of heat entirely into 100 J of work? A. only (i) is possible B. only (ii) is possible C. both (i) and (ii) are possible D. neither are possible

C

which of the following happens when a material undergoes a phase change A. the temperature changes B. the chemical composition changes C. heat flows into or out of the material D. the molecules break apart into atoms

C

A typical thermos bottle has a thin vacuum space between the shiny inner flask (which holds a liquid) and the shiny protective outer flask, often stainless steel. The vacuum space is excellent at preventing A. conduction B. convection C. radiation D. conduction and convection E. conduction, convection, and radiation

D

a heat engine operates between a high temperature of about 600 C and a low temperature of about 300 C. What is the maximum theoretical efficiency for this engine A. 100% B. 66% C. 50% D. 34%

D

an ideal gas undergoes an isothermal expansion from Tate A to state B. In this process A. Q=0, U=0, W>0 B. Q>0, U=0, W<0 C. Q=0, U>0, W>0 D. Q>0, U=0, W>0 E. Q=0, U<0, W<0

D

an ideal gas undergoes an isothermal process. Which of the following statements are true? (i) no heat is added to or removed from the gas (ii) the internal energy of the gas does not change (iii) the average kinetic energy of the molecules does not change A. (i) only B. (i) and (ii) only C. (i) and (iii) only D. (ii) and (iii) only E. (i), (ii), and (iii)

D

in an isobaric compression of an ideal gas A. no heat flows into the gas B. the internal energy of the gas remains constant C. no work is done on the gas D. work is done on the gas E. work is done by the gas

D

it has been a hot summer, so when you arrive at a lake, you decide to go for a swim even though it is nighttime. The water is cold! the next day, you go swimming again during the hottest part of the day, and even though the air is warmer the water is still almost as cold. Why? A. water is fairly dense compared with many other liquids B. water remains in a liquid state for a wide range of temperatures C. water has high bulk modulus D. water has a high specific heat

D

on a very hot day, could you cool your kitchen by leaving the refrigerator door open A. yes, but it would be very expensive B. yes, but only if the humidity is below 50% C. no, the refrigerator would exhaust the same amount of heat into the rooms it takes out of the room D. no, the heat exhausted by the refrigerator into the room is more than the heat the refrigerator takes out of the room

D

radiation is emitted A. only by glowing objects such as the sun B. only by objects whose temperature is greater than the temperature of the surroundings C. only by objects with more caloric than their surroundings D. by any object not at 0 K E. only by objects that have a large specific heat

D

the linear expansion of a material depends on which of the following? A. the length of the material B. the change in temperature of the material C. the type of material D. all of the above E. Both B and C

D

two objects are made of the same material, but they have different masses and temperatures. If the objects are brought into thermal contact, which one will have the greater temperature change? A. the one with the higher initial temperature B. the one with the lower initial temperature C. the one with the greater mass D. the one with the lesser mass E. the one with the higher specific heat

D

which of the following is not true about an ideal gas? A. the average kinetic energy of the gas molecules increases as the temperature increases B. the volume of an ideal gas increases with temperature if the pressure is held constant C. the pressure of an ideal gas increases with temperature if the volume is held constant D. all gas molecules have the same speed at a particular temperature E. the molecules are assumed to be far apart compared to their size

D

the temperature of an ideal gas increases. Which of the following is true? A. the pressure must decrease B. the pressure must increase C. the pressure must increase while the volume decreases D. the volume must increase while the pressure decreases E. the pressure, the volume, or both may, increase

E

two ideal gases, A and B, are at the same temperature. If the molecular mass of the molecules in gas A is twice that of the molecules in gas B, the molecules' root-mean-square speed is A. the same in both gases B. twice as great in A C. 1.4 times greater in A D. twice as great in B E. 1.4 times greater in B

E

a process in which no heat is allowed to flow into or out of the system. Q=0 so U=-W

adiabatic

as one end of an object is heated, the molecules there move faster and faster. As these faster molecules collide with slower-moving neighbors, they transfer some of their kinetic energy to them.

conduction

the process whereby heat flows by the bulk movement of molecules from one place to another

convection

latent heat of a substance transforming from solid to liquid

heat of fusion

latent heat of a substance changing from the liquid to the vapor phase

heat of vaporization

process in which the pressure is kept constant. Q=U+PV

isobaric

an idealized process, such as adding heat or doing work that is carried out at a constant temperature. Results in internal energy = 0 so Q=W

isothermal

process in which the volume does not change. W=0, so Q=U

isovolumetric

a type of heat transfer that occurs without any medium at all

radiation