Question 397, Principles of Flight (Balloon) - Quiz BPL Hot Air - Balloon Pilot License

At higher altitude, sink rate in case of cooling is increased due to less drag by less density.
At higher altitude, sink rate by cooling is not increased because due to low density the mass inside the hull is also less.
Higher drag at higher altitude prevents increased sink rate in case of cooling.
Maximum sink rate must be equal at all altitudes as prescribed by design regulations.