PHYS 221 SI Worksheet
1. (a) What is the average translational kinetic energy of a molecule of an ideal gas at a temperature of
27°C? (b) What is the total random translational kinetic energy of the molecules in one mole of this
gas? (c) What is the root-mean-square speed of oxygen molecules at this temperature? (One or more of
these may be useful: M = 32.0E-3 kg/mol, mass of one oxygen molecule = 53.1E-24 g, R = 8.314
J/mol·K.)
2. A thin square steel place, 10 cm on a side, is heated in to a temperature of 800°C. If the emissivity is
0.60, what is the total radiation of energy?
3. If the total surface area of the human body is 1.20 m2 and the surface temperature is 30°C, find the
total rate of radiation of energy from the body. If the surroundings are at a temperature of 20°C, what is
the net rate of heat loss from the body by radiation? The emissivity of the body is very close to unity,
irrespective of skin pigmentation.
4. In an automobile engine, a mixture of air and gasoline is compressed in the cylinders before being
ignited. A typical engine has a compression ratio of 9.00 to 1. The initial pressure is 1.00 atm and the
initial temperature is 27°C. If the pressure after compression is 21.7 atm, find the temperature of the
compressed gas.