Koshikudake (inadvertent collapse) – This is when a rikishi falls over backwards without his opponent attempting any technique. It often occurs when a rikishi overcommits to an attack. Koshikudake is recorded outside sumo's official list of winning techniques.

b) If the light is brighter, there will be more light energy converted into more kinetic energy and so, the vane will rotate faster.

c) As there was no more light source, there will, be no more light energy to be converted to kinetic energy and therefore, the vane will stop moving in a while.