Molecular Physics | Thermodynamics Answers

A capacitor is in series with a resistor and is charged to a potential of 100 V. When discharging the capacitor it takes 1.2 s for the potential across the capacitor to drop to 67 V. How long does it take the potential difference across the capacitor to drop to 30 V? (to 2 s.f and in s)

Define a constant pressure process and draw the P-V diagram for a constant pressure process 2.025k of fluid at a pressure of 3bar with a specific internal energy and specific volume of 2544kj/kg and 0.6057m³/kg respectively is heated at constant pressure until the specific internal energy is 2807kj/kg and volume is 0.2189m³. Calculate the work done and heat supplied? Hint:V²=V²/m.

In an air motor cylinder the compressed air has an internal energyof 450kg/kj at the beginning of the expansion and an internal energy of 220kg/kj after expansion. If the work done by air during the expansion is 120kg/kj,calculate the heat flow to and fro the cylinder and state if the system gain or losses heat

A steel cube has sides of length 20cm. Calculate its mass. (Density of steel = 7.7
g/cm 3 ). Give your answer in g, and in kg.

A particle vector is given by r=2ti+t^2j. Find: (a) r at t=1 and t=3, respectively;
(b) the displacement of particle from t=1 to t= 3.
(c) the path equation of the particle

What are the names and formulas of the conjugate bases of these acids: (a) HNO2, and (b) HCOOH (formic acid)?
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You are breathing at a rate of 20 breaths per minute in a warm, dry environment.
Each time you take a breath, you breathe in 0.5×10−3 kg of air at a temperature of 24°C and with a relative humidity of 20%. You breathe out the same mass of air but at a temperature of 36°C and a relative humidity of 100%.
How much water vapour do you exhale in one hour under these circumstances? (to 2 s.f and in g)

A furnace wall consists of 250 mm firebrick,125 mm insulating brick, and 250 mm building block.The inside wall is at a temperature of 600°C and the atmospheric temperature is 20°C.The heat transfer coefficient of the outside wall is 10 W/m2k, and the thermal conductivities of the fire brick, insulating brick, building brick are 1.4, 0.2, 0.7 W/m k respectively. Neglecting radiation, calculate the rate of the Heat Loss per unit wall surface area, and the temperature of the outside wall suface of the furnace.
[ANS:460 W/m2;60°C]

A 1.5 kg block of wood and a 2.5 kg block of steel are placed in thermal contact.
If the wood was at an initial temperature of 50°C and the steel was at an initial temperature of 15°C then what is the final equilibrium temperature of the wood and steel? (to 2 s.f and in °C)
[cwood = 2400 J kg−1 K−1, csteel = 490 J kg−1 K−1]

The 1.0-m-tall cylinder in FIGURE P14.61 contains air at a pressure of 1 atm. A very thin, frictionless piston of negligible mass is placed at the top of the cylinder, to prevent any air from escaping, then mercury is slowly poured into the cylinder until no more can be added without the cylinder overflowing. What is the height h of the column of compressed air?

Hint: Boyle’s law, which you learned in chemistry, says for a gas compressed at constant temperature, which we will assume to be the case.