Pre-U Review - Thermal Physics

The energies of air in a moving aircraft are as follows:

8 MJ of kinetic energy as a result of the motion of the aircraft,

30 MJ of kinetic energy as a result of the random movement of the air molecules,

75 MJ of potential energy as a result of the altitude of the aircraft,

-3 MJ of potential energy as a result of intermolecular attraction between the air molecules.

Which of the following is the internal energy of the air in the aircraft?

• 27 MJ

• 33 MJ

• 35 MJ

• 110 MJ

The walls of an enclosure is maintained at a steady temperature T. When two thermometers are placed inside the enclosure, they give the same reading T after thermal equilibrium has been established.

Which statement correctly describes the required conditions?

• under all circumstances

• only if they absorb radiation at equal rates

• only if both are perfect absorbers

• only if they have equal thermal capacities

Two bodies, X and Y, are in thermal equilibrium. Body Y is also at the same temperature as a third body Z. The three bodies are of different materials and have different masses.

Which statement must be correct?

• X and Y have the same heat capacity

• Y and Z have the same internal energy

• There is no net transfer of energy if X is placed in thermal contact with Z

• It is not necessary that Y should be in thermal equilibrium with Z

• 20 °C

• 30 °C

• 70 °C

• 80 °C

The values p_steam and p_ice of a quantity p at the steam and ice-points were determined and divided into one hundred equal divisions to form an empirical centigrade scale of temperature.

Which equation gives the centigrade temperature t on the scale of that thermometer when the quantity p has a value p_t ?

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When its temperature is at the triple point of water, a fixed mass of gas in a gas thermometer has pressure p(tr) = 1.00 x 10⁵ Pa and volume V(tr) = 1.00 x 10^-3 m³.

What is the temperature of the gas when its pressure is 1.10 x 10⁵ Pa and its volume 1.20 x 10^-3 m³?

• 207 K

• 250 K

• 273 K

• 361 K

For a sample of a real gas at a given temperature, the pressure p and volume V are measured for various pressures. The given graph shows the relationship between the product pV and p for three different temperatures; the triple point of water, the boiling point of water, and T, an unknown thermodynamic temperature between the two.

What is the value of T?

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On the Celsius scale, the temperature of an object at 100 °C is increased by Δθ. What is this temperature change when expressed on the Kelvin scale?

• Δθ + 373

• Δθ + 273

• Δθ + 100

• Δθ

What is the temperature on the Celsius scale that is equivalent to 273.00 K?

• -0.15 °C

• 0.00 °C

• 0.15 °C

• 273.15 °C

Which of the following best explains why the triple point of water, rather than the melting point of ice, has been selected as the fixed point for the establishment of the kelvin?

• it is more precisely reproducible

• it is closer to the defining temperature 273.16 K

• it gives a more convenient scale between 0 °C and 100 °C

• very accurate gas thermometers have shown that it is better