# Need help with a calculus problem?

• dontdisturbmycircles

#### dontdisturbmycircles

Try http://www.mathcasts.org/db_calc/main_view.php .

I just did a google search for a specific type of problem I was struggling with and this website helped a lot. I can't guarantee that all the videos are accurate, but there are lots of them(note that there are 6 pages) and they seem fine to me.

Enjoy.

Find the topic you are interested in and click "mathcast".

Even though they are geared towards a specific textbook, its all the same stuff so if you are stuck on an topic, you may be able to find info about it here.

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Thanks dontdisturbmycircles for the kind words about the mathcasts and thanks minase for noticing the dead links - which hopefully are now fixed! LFS

Dear god, she did a problem with a constant voltage ('electric pressure')

What the...'electric pressure'.....sigh...

Systems Dynamics

Cyrus:

In Systems Dynamics 101, any system can be described using equations whereby an EFFORT variable induces a FLOW variable. These equations are usually only to 2nd order (2nd derivative.)

Some examples: Electrical voltage induces a current; current is affected by resistance. Pressure difference induces fluid flow -- which is affected by pipe friction. Temperature difference induces heat transfer -- which is affected by insulation. Difference of forces induces motion -- which is affected by rolling (or sliding) friction. Similarly for rotational momentum systems, diffusion systems, or any other system.

Make a chart of these various systems, their effort and flow variables and the governing equations for each. You will understand what she meant by "electrical pressure." BTW, it is common to use fluid flow analogies to describe electrical systems, and vice versa.