Molecular Physics | Thermodynamics Answers

A steel railroad track has length of 30m when the temperature is 0 degrees (a) when the temperature is 40 degrees, what is it’s length. (b) if the end of the rail are rigidly clamped at 0.0 degrees so that the expansion is prevented, what is the thermal stress set up if the rail is raised to 40 degrees

Q 4. A 0.5 kg of aluminum cube at 27 ℃ and a 1.0 kg of copper cube at 100 ℃ are placed 

in 2 kg of water at 22 ℃. Assuming no heat loss to the surroundings, calculate the final 

temperature of the mixture.

Specific heat capacities: water 𝑐𝑊 = 4187 𝐽𝑘𝑔−1𝐾

−1

, copper 𝑐𝑐𝑢 = 386 𝐽𝑘𝑔−1𝐾

−1

, 

aluminum 𝑐𝑎𝑙 = 900 𝐽𝑘𝑔−1𝐾

−1

Q 5. A 5 kg of ice cube at −10℃ is mixed with 0.1 kg of water at 80 ℃. There is no heat 

loss to the surrounding. The specific heat capacity of ice is 2.22 𝑘𝐽𝐾

−1𝑘𝑔−1

,The specific 

heat capacity of water is 4.187 𝑘𝐽𝐾

−1𝑘𝑔−1

. The specific latent heat of fusion of ice is 

333 𝑘𝐽 𝑘𝑔−1

.

(a) What is the final physical state of the mixture? (Gas, Liquid or Solid?)

Justify your answer using suitable calculations 

(b) What is the final temperature of the mixture?

A mercury-glass thermometer consists of a glass bulb filled with mercury and a 

narrow glass tube attached to the glass bulb. At 0℃, the bulb is completely filled with the 

mercury and its radius is 5 mm. As the temperature increases the mercury column rise 

through the narrow glass tube whose diameter is 0.3 mm. 

What should be the minimum length of the glass tube so that this thermometer can be 

used to measure the temperatures up to 100 ℃ ?

(Hint: ignore the thermal expansion of the glass tube)

liner expansion coefficient of glass = 3.2 × 10−6 ℃−1

volume expansion coefficient of mercury = 1.82 × 10−4 ℃−1

Assume 2 kg of hydrogen (Item B 28) are initially at 40 atm, 100 K. (a) If the hydrogen changes pressure to 1 atm without a change of temperature, find the changes of enthalpy and entropy. (b) If the hydrogen changes temperature to 35 K with no change of entropy, find the change of pressure and enthalpy.

A nozzle is a device for increasing the velocity of a steadily flowing stream. At the inlet to

a certain nozzle, the enthalpy of the fluid passing is 3000 kJ/kg and the velocity is 60 m/s.

At the discharge end, the enthalpy is 2762 kJ/kg. The nozzle is horizontal and there is

negligible heat loss from it. (a) Find the velocity at exists from the nozzle. (b) If the inlet

area is 0.1 m2 and the specific volume at inlet is 0.187 m3

/kg, find the mass flow rate.

(c) If the specific volume at the nozzle exit is 0.498 m3

/kg, find the exit area of the nozzle.

During the execution of a reversible nonflow process where the volume changes 

from an initial volume is 0.845 m3

to a final volume of 0.28 m2

and the pressure varies 

as p = -730V + 690 kPaa, where V is in m3

. Determine the work done

Steam flows through an adiabatic turbine at the rate of 100 lb/min with KE = 0

and Q = 0. At entry , its pressure is 175 psia , its volume is 3.16 ft3

/ lb and its internal

energy is 1166.7 BTU / lb. At the exit, its pressure is 0.813 psia, its volume is 328 ft3

/lb

and its internal energy is 854.6 BTU / lb. What horsepower is developed

Suppose that the steel gas tank in your car is completely filled when the temperature is 16 °C. How many gallons will spill out of the 88-Liters tank when the temperature rises to 40 °C?

A football is kicked vertically upward from the ground and a student gazing out of a window sees it coming passed him at 16ft/sec. The window is 30ft above the ground.

a. How high does the ball go above the ground?

b. How long does it take to go from a height of 30ft to the highest point?

liquid ammonia at a temperature of 26 celcius available at the expansion valve, undergoes isenthalpic process until its temperature becomes 2 degree celcius. find the percentage of liquid vaporized while lowing through the expansion valve