El tagadá tiene una frecuencia de 100Hz constante ¿Cuántos ciclos cumplirá en 15 minutos? ¿Qué periodo tiene el tagadá?

its not a choice. you dont choose if you want to be gay or straight.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.