How does mass affect gravity

The speed of light in a material is 0.50 c. what is the critical angle of a light ray at the interface between the material and a vacuum?

Atwo-stage air compressor operates at steady state, compression 10m^3/min of air from 100 kpa and 300k to 1200 kpa. an intercooler between the two stages cools the air to 300k at a constant pressure of 350 kpa. the compression processes are isentropic. a) calculate the power required to run the compressor, in kw b) compare the result to the power required for isentropic compression from the same inlet state to the same final pressure.

If a tank filled with water contains a block and the height of the water above point a within the block is 0.8 meter, what is the pressure at point a?