Of course steady state condition occurs in almost any system but time it will occurs varies among system. for this kind of system, conduction, steady state conduction occurs when the temperature change from one point to the point is already constant. steady state is not achieved immediately because the heat travels and material will not be heated at the same way at the starting point.
Answer:
There is no change, unless your mass is somehow at the quantum level, at which the concept of half-life breaks down.
Half life is a property of the specific radioactive isotope...NOT of the initial sample's mass.
Gravitational potential energy.
As the rider falls, the GPE is converted into kinetic energy.