# Exactly what is there to understand in physics? Its memory?

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1. Feb 22, 2015

### x86

I notice a lot of people say that physics is all understanding. But to me it seems like useless memorization of formulas (as opposed to say real analysis). I will give an example over here, with my thought process. Perhaps someone who disagrees with me can tell me their thought process, and this may forever change my mind.

For instance, impulse. Okay, we note that F = ma = m dv/dt. If we take the intergral of Fdt = m dv then we get Impulse = m (delta)v or mv1 + impulse = mv2

Now we notice that we can use this formula to solve problems which we could solve using other kinematic equations. Memorize this formula, so that when you're given a question like this on the test, you can solve it.

To me, things like this really have nothing to understand, it just seems like another formula to memorize. Especially when derivations get much more complicated. You don't have time to actually think about problems on tests, more so than writing down the formulas you've memorized which you think you can use.

Am I wrong, or is physics essentially just 100% memorizing formulas and figuring out which one to use to solve a problem?

2. Feb 22, 2015

### Bystander

Memorization of definitions, yes. You have to "know" what you're analyzing. Once the definitions become part of your "analytical vocabulary, tool belt, whatever," you'll get to the point where you can frame your own questions, write your own problem statements, and begin understanding the world around you.

3. Feb 22, 2015

### PeroK

What you've described is the way a lot of students try to do physics - and, perhaps, the way it is often taught.

I've helped a few people with homework on here now and one of the key pieces of advice would be to understand the problem first before thinking about any formulas. The first step is to understand the problem and the second step is to solve it, using whatever formulas and techniques you have.

Also, memorising things is a lot easier when you understand why things are so. In fact, it hardly seems like memorising. Here's a good example:

If you take a chess board and set up a position, a good player can "memorise" it very quickly. And a non-player can't memorise it at all.

But, if you just put the pieces on the board at random, the good player can no longer memorise much better than the non-player. This is because the position no longer "makes sense".

In other words, if you try to memorise things as simply a sequence of random symbols, life's going to be tough. But, if you understand the physics, the "memorisation" comes at little extra effort.

4. Feb 22, 2015

### zoki85

What do you think how people come up with formulas?

5. Feb 22, 2015

### A.T.

Nah, that's what books and the internet are for.

That is the key part of engineering. Physics is more about coming up with new formulas.

6. Feb 22, 2015

### Staff: Mentor

Physics starts to get interesting at the point where you have to find your own formulas, or at least modify existing formulas to fit your problem or use existing formulas in new ways.

7. Feb 22, 2015

### Teichii492

There was a time I briefly felt this way and also i see this line of thinking in many other students i have encountered. My first statement would be that, at least where I'm from, this appears to be the aim of the majority of science classrooms at an elementary level (high school), however much the teacher would like to have the students understand the material there are ostensibly many students in those classrooms who have little interest in the understanding of the material (since these classes are compulsory) and more worry about their grades, it isn't helped by a pressure put on teachers by grade based performance.

As you progress through the hierarchy of education levels you tend to find that being able to simply analyze a question for useful numbers and plug them into an equation less and less relevant.

I have noticed (being only an undergraduate at the moment) that those who have allowed themselves to become entrenched in this way of thinking do not fare as well (in their mental state in regards to the course) as those who wish to understand. It is the attitude of simply looking to get the good grades and then get a good job that have been engrained into some students by a society that constantly emphases the importance of these aspects of learning. They often forget that a passion for the subject and therefore the need to understand it should come first and then good grades and perhaps a well-paying job will follow.

It helps with expediency if you memorize formulas, and even more so would be physical constants. Then you can spend more test time with your analysis of the question and understanding it, rather than looking up formulas and constants in a book. Although, after a decent amount of practice you tend to have these formulas and constants engrained unwillingly into your memory.

You must acknowledge that even being able to read a simple mechanics question and plug the numbers given into an equation requires some basic understanding of the question even if these are as elementary as where the force is, or what a certain word in the question translates to as a symbol in your equation.

Derivations at a higher level of education most definitely require a fundamental understanding of the nature of the physical process as opposed to just memorization. Take for example a derivation that every undergraduate physics student will learn, time dilation. However simple it is mathematically, it requires you to understand the assumptions and understand the physical situation.

Test questions at the university level are designed in a way (at least in my experience) that is aimed specifically at weeding out those who think like this, and identifying and emphasizing the importance of understanding over memorization. Although, if you want to get semantic, all 'understanding' is an offshoot of 'memorization' since after countless problem solving, you find yourself able to instantly recall certain relationships between physical situations and equations.
As this gets more advanced you find that the symbols in an equation represents more symbols from more elementary equations and then they can take you back to your derivation which usually has an analogous physical situation attached to it in your memory.
It is these connections that as you progress in your understanding of the different areas of physics will give you little moments of elucidation, where you suddenly can connect one physical idea to another independent of being told about that connection.

I expect that it in some neurological way it is this formation of connections that can lead to a much higher understanding of a subject to the point where you are able to make connections between complex mathematics and the physical universe in a way that opens up new avenues of thought and leads to developments in science as a whole.

I'll go ahead and agree with you by saying that to the majority of students at the lower levels of education it may seem this way and i think it's a problem that needs some investigation and thought into possibly remedies. Although, it's possible that it's simply a case of lack of motivation for some and neurological condition resulting from a combination of societal pressures and perhaps bad teaching methods for others.

8. Feb 22, 2015

### Staff: Mentor

There are just two formulas I learned via "okay, here is the formula and I'll learn it now" - for a mathematics exam, and I forgot them again afterwards. All the physics equations I know I learned by deriving them, understanding them, or at least applying them often enough. It takes more time initially, but it makes physics problems so much easier if you understand equations instead of just knowing them.
There is an "understanding" part that goes beyong memorization. Sure, it helps if you saw similar problems in the past, but once you go beyond the standard textbook equations you have to understand the problem. And this understanding can be trained.

9. Feb 22, 2015