En que tipos de movimiento la gravedad es la aceleración?

Tungsten-filament lightbulb emits light based on the temperature of the filament. which phenomenon does this demonstrate?

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

In a set amount of time, a battery supplies 25j of energy to an electric circuit that includes two different loads. one of the loads produces 10 j of heat energy during this time interval. how much heat energy is produced by the second load in this time? explain your answer