the heat produced by 3 kg of fuel a is 50000 J the heat produced by 5 kg of fuel b is 3000 KJ which fuel is more efficient

14 days is the half-life of phosphorus-32

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.