# Where is the bridge between Calculus and Physics?

I am soooo lost. I don't even know if this is the right forum. But where is the bridge between Calculus and Physics? I can Integrate equations, but when it comes to physics, i for one, don't know when to integrate; two, i don't see how you find the constants to remove from the integral; and three, Even given the integral formula for an equation, i still don't know what im doing.

ex. Va-Vb=SE.dl

S-integral
E-Electric Field
dl-small segments of length

I don't know how to use the equation;

Or, electric flux,

Flux=SE . dA

What am i not understanding. Please help

## Answers and Replies

LCKurtz
Science Advisor
Homework Helper
Gold Member

I would say you might want to review your Calc III notes about line integrals and flux integrals. You might have seen them in the following forms in your calculus class:

$$\int_C \vec F \cdot d\vec R$$

$$\int\int_S \vec F \cdot d\vec S$$

Pardon me for changing the subject but in this post I want to test putting a graphic in my post. If it works you should see bugs bunny.

http://math.asu.edu/~kurtz/bugs.gif

sry to disappoint... but, no bugs bunny. lol

what if i said i just started calculus II about a month ago. I can do integrals by sub, parts, but im not seeing where they are used.

LCKurtz
Science Advisor
Homework Helper
Gold Member

sry to disappoint... but, no bugs bunny. lol

what if i said i just started calculus II about a month ago. I can do integrals by sub, parts, but im not seeing where they are used.

The integrals you are seeing in your class are generally introduced in calc III. So I would say you aren't ready for that Physics class yet because you don't have the proper prerequisites.

I am soooo lost. I don't even know if this is the right forum. But where is the bridge between Calculus and Physics? I can Integrate equations, but when it comes to physics, i for one, don't know when to integrate; two, i don't see how you find the constants to remove from the integral; and three, Even given the integral formula for an equation, i still don't know what im doing.

ex. Va-Vb=SE.dl

S-integral
E-Electric Field
dl-small segments of length

I don't know how to use the equation;

Or, electric flux,

Flux=SE . dA

What am i not understanding. Please help

I'm assuming you are still in freshman physics classes. Unless your school is extremely competitive, you are not going to need to apply calculus seriously until your junior year. These questions you ask are extremely fundamental to success in physics once you reach that level however. I recommend you find a helpful professor to ask these questions of. These are the questions which are supposed to be answered by your calculus and physics classes.

so your equation:
$$V_{2} - V_{1} = \int E \cdot dl$$

Is a consequence of the fundamental theorem of line integrals which you should of met in one of your previous calc courses. What it says is that if your vector field (in this case the electric field) can be written in terms of the gradient (the grad function from your calc courses) of some scalar potential (in this case your voltage). then the line integral of the vector field from point A to point B is equall to the difference of your scalar potential at points A and B.

I can sympathise with making that jump from relatively abstract calculus (esp integration) to applying it to physical problems - but as everyone else in the thread has said, if the maths that I've tried to explain is new to you then you may need to take a couple more calculus courses before you try and tackle this stuff.