Name two of the four common boundry conditions we set when disucssing gravitational potential energy? It's an open-ended question.
I'm a little confused as to what they mean by "Boundry Conditions" I answered last time " Acceleration due to gravity, and distance". I only got one of those right... Im still confused.. can someone help me please!?!?!?

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.

4. if you were an astronaut on the moon, what would you experience? what would you see from your perspective?

What is the relationship between the direction of motion of the balloon and the wind currents