Making assumptions and approximations are a critical part of scientific modeling. The real world is very complex, so we are often creating a simplified model to explain, predict, and describe physical phenomena. Assumptions and approximations are a critical part of this process because they highlight what you are considering relevant and what you are considering as unimportant or negligible.

Despite being very important, they are often not talked about in depth or are only mentioned as a side note. So in this class we are explicitly trying to highlight the assumptions part of the model and practice identifying/recognizing the assumptions that we use in our problems. Determining those assumptions and approximations can be very challenging. There is not one right answer because the assumptions are highly context dependent and each problem will take a critical examination of that situation.

This page of notes will outline some general strategies for thinking about assumptions and provide a couple of examples based on problems that we've done in class so far.

There are many different reasons why you might need to make an assumption. Below we've listed out three big reasons you'll frequently run into in the Main Problems in class.

In complex, real world problems, there are often multiple quantities that you do not know. The same is true of our in class problems. When you multiple variables that you do not know, you have a decision to make as to what values to assume and what you are going to solve for. For example in the very first problem in class (1A: Chasing Thunderclouds), you were missing the electric field value, the charge, and the cloud height. One way to solve that problem is to calculate the E-field, and then make assumptions about the charge of the cloud and the cloud height.

If we think particularly about the cloud height assumption, there are several ways we could think about picking a value for the cloud height:

• The realistic scenario -
• The average situation -
• The worst case scenario -

All of these methods involve looking up some information online, but the second crucial step is to think critically about the values that you find online and how they might relate to your goal in the problem and the context that your given.