2
v7x10-3 m)
2. (25 marks) (a) use the ideal gas law to estimate the number of air molecules in
your physics lab room, assuming all the air is n2. the room size is 150m”, the
temperature is 20°c, the pressure is latm. (b) calculate the particle density in the lab
(that is, the number of molecules per cubic meter)

Asheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200oc and is permitted to achieve a steady-state diffusion condition. the diffusion coefficient for nitrogen in steel at this temperature is 6 x 10- 11 m2 /s, and the diffusion flux is found to be 1.2 x 10-7 kg/m2 -s. also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m3 . how far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3 ? assume a linear concentration profile.

What is the orbital period of a spacecraft in a low orbit near the surface of mars? the radius of mars is 3.4×106m.

Which statement is true if the refractive index of medium a is greater than that of medium b? a. total internal reflection is possible when light travels from air to medium b to medium a. b. total internal reflection is possible when light travels from medium a to medium b. c. total internal reflection is possible when light travels from medium b to medium a. d. total internal reflection is possible when light travels from air to medium a. e. total internal reflection is possible when light travels from air to medium b.