The rise in temperature of an iron when dropped from a height of 900 meters cannot be accurately determined without additional information. The change in temperature would depend on various factors such as the initial temperature of the iron, its specific heat capacity, the surrounding environment, and the time it takes for the iron to reach the ground.
When an object falls from a height, its potential energy is converted into kinetic energy, and some of this energy is dissipated as heat due to air resistance. However, the amount of heat generated is generally negligible compared to the mass and heat capacity of the object.
To calculate the change in temperature accurately, you would need detailed information about the specific heat capacity of the iron, the surface area of the object, the velocity at impact, and the thermal conductivity of the surrounding air. Without this information, it is not possible to provide a precise estimation of the temperature rise.