Molecular Physics | Thermodynamics Answers

1. Explain in 15 words only, why an ice cube at 0 ˚C is more effective in cooling a drink than
the same mass of water also at 0 ˚C. (3 marks)
2. A woman is unhappy with the rate at which eggs cook in a saucepan of boiling water. State
in 2 words only, the method she could use to get the eggs to cook fastest. (2 marks)
3. A faulty mercury-in-glass thermometer indicates that the ice point of pure water is 0.8 ˚C
and the steam point 99.5 ˚C under standard atmospheric pressure. Deduce an expression in
the form of y = mx + c, where m and c are constants, to relate the faulty temperature reading
F ˚C to the correct temperature T ˚C. (3 marks)
4. Using the equation deduced in Question 3 above, calculate the correct temperatures when
the faulty thermometer reads -15 ˚C and 50 ˚C.

You have been asked to design an appliance for a water supply pumping station. The
appliance will operate using a tree plantation as starting source of energy and the following
supplies only; a steam-powered electric generator, water pump and a light-activated siren
system. Use a flow chart of 7 (seven) items only to describe the sequential energy
conversions to be anticipated. (14 marks)
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A glass Louvre pane 0.4 cm thick has an area 2×10^4 cm^2. On a very cold day the temperature difference between the inside and the outside surfaces of the pane is 25 degree Celsius determine the heat flow through the window

12kg of a fluid per minutes goes through a reversible steady flow process. The properties of the fluid at inlet are p1=1.4bar, P1=25kg\m3 C1= 120m\s, U1=920kj\kg and at the exit p2=5.6kg\m3,C2=180m\s,P25kg\m3,U2=720kg\kg. During the passage the fluid rejects 60m. Determine the change in enthalpy and work done during the process

An air conditioner is working at 293 K in a room. What
macroscopic and microscopic parameters are involved,
if room is filled with normal air?

An air conditioner is working at 293K in a room. What macroscopic and microscopic parameters are involved, if room is filled with normal air?

A nozzle is a device for increasing the velocity of a steadily flowing stream of fluid. At the inlet to a certain nozzle the enthalpy of the fluid is 3025kj/kg and the velocity is 60m/s. At the exit from the nozzles the enthalpy is 2790kj/kg.The nozzle is horizontal and there is negligible heat loss from it.
(i) Find the velocity at the nozzle exit.
(ii) If the inlet area is 0.1m^2 and the specific volume at the inlet is 0.19m^3/kg. Find the rate of flow of fluid.
(ii) If the specific volume at the nozzle exit is 0.5m^3/kg. Find the exit area of the nozzle

75600J of thermal energy is needed to raise the temperature of a 2.0kg block of ice removed from a freezer at −18∘C to its melting point. Calculate the specific heat capacity.

A turbine operating under steady flow condition receives 5000kg of steam per hour. The steam enter the turbine at a velocity of 3000m/min, an elevation of 5m and a specific enthalpy of 2787kj/kg, it leaves from the turbine at a velocity of 6000m/min an elevation of 1m and a specific enthalpy of 2259kj/kg. Heat losses from the turbine to the surrounding amount to 16736kj/h
Determine the power output of the turbine

In the turbine of a gas turbine unit the gases flow through the turbine is 17kg/s and the power developed by the turbine is 14000kw. The enthalpies of the gases at inlet and outlet are 1200kj/kg and 360kj/kg respectively and the velocity of the gases at inlet and outlet are 60m/s and 150m/s respectively
Calculate the rate as which the heat is rejected from the turbine. Fine also the area of inlet pipe given that the specific volume of the gases at inlet is 0.5m³/kg