Physics 2 Chapters 14-16

After 5 minutes the sample was a mixture of solid and liquid.

A solid sample of a pure compound is contained in a closed, well-insulated container. Heat is added at a constant rate and the sample temperature is recorded. The resulting data is graphed in the figure below. Which of the following conclusions is justified from the graph shown?

2v

An ideal gas is held in a container of volume V at pressure P. The rms speed of a gas molecule under these conditions is v. If now the volume and pressure are changed to 2V and 2P, the rms speed of a molecule will be ? .

no engine can be more efficient than a Carnot engine operating between the same two temperatures.

An important feature of the Carnot cycle is that ? . 1. its efficiency depends only on the absolute temperature of the hot reservoir used. 2. its efficiency is determined by the temperatures of the hot and cold reservoirs between which it works and by the properties of the working substance used, and on nothing else. 3. it is an example of an irreversible process that can be analyzed exactly without approximations. 4. its efficiency can be 100%. 5. no engine can be more efficient than a Carnot engine operating between the same two temperatures.

temperature

For an ideal gas the internal energy U depends only on ? .

the one with the curved under slope

From the figure below, an architect is interested in estimating the heat loss (in kcal/sec) through a sheet of insulating material as a function of the thickness of the sheet. Assuming fixed temperatures on the two faces of the sheet, which of the graphs best represents the heat transfer as a function of the thickness of the insulating sheet?

specific heat

If you wanted to know how much the temperature of a particular piece of material would rise when a known amount of heat was added to it, which of the following would be most helpful to know?

n is the number of moles of gas.

In the equation pV = nRT, ? .

The work done in the process is equal to the area enclosed by the cyclic process.

In the figure below is a cyclic process carried out in a gas. Which of the following is an accurate statement?

yes, it would probably work because the black surface would be a better absorber of sunlight than would the white snow.

In years of heavy snow pack in the mountains it is sometimes desirable to induce early melting of the snow, rather than wait until it all melts suddenly and causes floods. It has been suggested that a way to accomplish this might be to have planes fly over the snow fields and sprinkle them with black soot. What do you think of this idea? Would it work?

different metals have different thermal expansion coefficients

Shown below is a device that can be used to turn a furnace on or off, depending on the temperature sensed by the device. From the figure above, the principle underlying the operation of this device is that ? .

depends only on the temperature of the gas, and not on pressure or volume

The internal energy of an ideal gas ? .

increases

When an ideal gas is expanded in volume at constant pressure, the average kinetic energy of the gas molecules ? .

The entropy of an isolated system is conserved, i.e. constant.

Which of the following is a FALSE statement? 1. The total entropy change in one cycle of a Carnot engine is zero. 2. Entropy can be measured in units of J/K. 3. The entropy of an isolated system is conserved, i.e. constant. 4. Entropy is a quantitative measure of disorder.

The heat added to an ideal gas during the transition from state 1 to state 2 depends only on the initial and final states, 1 and 2, and not on the path by which the gas went from one to the other.

Which of the following is a FALSE statement? 1. When an ideal gas experiences a free expansion, its temperature doesn't change. 2. When a gas goes from one state to another, the work done depends on the path followed. Heat is energy transferred into or out of a system as a result of a temperature difference between the system and its surroundings. 3. The heat added to an ideal gas during the transition from state 1 to state 2 depends only on the initial and final states, 1 and 2, and not on the path by which the gas went from one to the other. 4. It does not make sense to refer to "the amount of heat in a body."

All of these are are false

Which of the following is a TRUE statement? 1. All of these statements are false. 2. It is possible for heat to flow spontaneously from a hot body to a cold one or from a cold one to a hot one, depending on whether or not the process is reversible or irreversible. 3. It is impossible to transfer heat from a cooler to a hotter body. 4. It is not possible to convert work entirely into heat. 5. The second law of thermodynamics is a consequence of the first law of thermodynamics.

In some regions the following sign is frequently seen as one approaches a bridge: "CAUTION: BRIDGE MAY BE ICY". One reason you might expect a bridge to be icier than the road leading up to it is that the bridge has both its top and bottom exposed to cold air, whereas only the top surface of the road is in contact with cold air.

Which of the following is a true statement? 1. Thermos bottles have a vacuum between the inner and outer layers of glass in order to reduce heat transfer due to radiation, since radiation cannot travel through a vacuum. 2, In some regions the following sign is frequently seen as one approaches a bridge: "CAUTION: BRIDGE MAY BE ICY". One reason you might expect a bridge to be icier than the road leading up to it is that the bridge has both its top and bottom exposed to cold air, whereas only the top surface of the road is in contact with cold air. 3. When the metal cooling coils in a freezer become coated with ice this helps the freezer more effectively remove heat from warm foods placed in the freezer. 4. When you get out of a swimming pool and stand dripping wet in a breeze you feel colder than you would if your skin were dry. This is a purely psychological effect, since measurement of your skin temperature would yield the same value in both cases, wet or dry. 5. Several days after a snowstorm, the roof on Jones's house is uniformly covered with snow, whereas on Smith's house next door the snow has completely melted off. A likely reason for this is that Smith's house has better roof insulation than does Jones's.

e = 1 - (Qc/Qh) e = (Qh-Qc)/Qh e = W/Qh

Which of the following relationships are true for all types of heat engines?

540 calories of heat are required to evaporate each gram of water from your skin, and most of this heat flows out of your body.

You may have noticed that when you get out of a swimming pool and stand dripping wet in a light breeze, you feel much colder than you feel after you dry off. Why is this?